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	$172.53	10.523%	$190.6853	$190.69	$190.70	$190.70
Purchase #2	$189.65	7.423%	$203.7277	$203.73	$203.75	$203.70
Purchase #3	$200.57	6.129%	$212.8629	$212.86	$212.85	$212.90
Purchase #4	$71.89	9.216%	$78.5154	$78.52	$78.50	$78.50
Purchase #5	$62.27	5.540%	$65.7198	$65.72	$65.70	$65.70
Purchase #6	$125.79	3.237%	$129.8618	$129.86	$129.85	$129.90
Purchase #7	$242.30	11.128%	$269.2631	$269.26	$269.25	$269.30
7 purchase totals =	$1,065.00		$1,150.6360	$1,150.64	$1,150.60	$1,150.70