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	$243.44	10.755%	$269.622	$269.62	$269.60	$269.60
Purchase #2	$68.72	8.476%	$74.5447	$74.54	$74.55	$74.50
Purchase #3	$59.78	9.663%	$65.5565	$65.56	$65.55	$65.60
Purchase #4	$195.93	10.674%	$216.8436	$216.84	$216.85	$216.80
Purchase #5	$198.98	3.411%	$205.7672	$205.77	$205.75	$205.80
Purchase #6	$56.50	3.577%	$58.521	$58.52	$58.50	$58.50
Purchase #7	$82.73	3.367%	$85.5155	$85.52	$85.50	$85.50
7 purchase totals =	$906.08		$976.3705	$976.37	$976.30	$976.30