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	$99.28	3.193%	$102.45	$102.45	$102.45	$102.50
Purchase #2	$69.98	13.368%	$79.3349	$79.33	$79.35	$79.30
Purchase #3	$145.26	4.155%	$151.2956	$151.30	$151.30	$151.30
Purchase #4	$185.47	8.315%	$200.8918	$200.89	$200.90	$200.90
Purchase #5	$223.88	12.235%	$251.2717	$251.27	$251.25	$251.30
Purchase #6	$78.75	6.224%	$83.6514	$83.65	$83.65	$83.70
Purchase #7	$59.92	4.780%	$62.7842	$62.78	$62.80	$62.80
7 purchase totals =	$862.54		$931.6796	$931.67	$931.70	$931.80