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	$92.92	7.373%	$99.771	$99.77	$99.75	$99.80
Purchase #2	$32.62	6.184%	$34.6372	$34.64	$34.65	$34.60
Purchase #3	$175.84	5.746%	$185.9438	$185.94	$185.95	$185.90
Purchase #4	$189.61	5.656%	$200.3343	$200.33	$200.35	$200.30
Purchase #5	$52.89	13.605%	$60.0857	$60.09	$60.10	$60.10
Purchase #6	$181.57	5.675%	$191.8741	$191.87	$191.85	$191.90
Purchase #7	$144.77	6.747%	$154.5376	$154.54	$154.55	$154.50
7 purchase totals =	$870.22		$927.1837	$927.18	$927.20	$927.10