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	$52.45	8.197%	$56.7493	$56.75	$56.75	$56.70
Purchase #2	$143.45	3.325%	$148.2197	$148.22	$148.20	$148.20
Purchase #3	$48.89	13.814%	$55.6437	$55.64	$55.65	$55.60
Purchase #4	$49.56	6.346%	$52.7051	$52.71	$52.70	$52.70
Purchase #5	$146.99	6.279%	$156.2195	$156.22	$156.20	$156.20
Purchase #6	$154.30	12.841%	$174.1137	$174.11	$174.10	$174.10
Purchase #7	$134.61	8.689%	$146.3063	$146.31	$146.30	$146.30
7 purchase totals =	$730.25		$789.9573	$789.96	$789.90	$789.80