Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$249.49	11.713%	$278.7128	$278.71	$278.70	$278.70
Purchase #2	$220.47	13.481%	$250.1916	$250.19	$250.20	$250.20
Purchase #3	$166.65	8.383%	$180.6203	$180.62	$180.60	$180.60
Purchase #4	$199.65	11.627%	$222.8633	$222.86	$222.85	$222.90
Purchase #5	$152.41	10.559%	$168.503	$168.50	$168.50	$168.50
Purchase #6	$215.56	8.332%	$233.5205	$233.52	$233.50	$233.50
Purchase #7	$210.90	8.453%	$228.7274	$228.73	$228.75	$228.70
7 purchase totals =	$1,415.13		$1,563.1389	$1,563.13	$1,563.10	$1,563.10