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	$57.57	5.456%	$60.711	$60.71	$60.70	$60.70
Purchase #2	$168.26	9.136%	$183.6322	$183.63	$183.65	$183.60
Purchase #3	$149.50	6.700%	$159.5165	$159.52	$159.50	$159.50
Purchase #4	$145.54	10.462%	$160.7664	$160.77	$160.75	$160.80
Purchase #5	$89.41	10.792%	$99.0591	$99.06	$99.05	$99.10
Purchase #6	$17.99	8.419%	$19.5046	$19.50	$19.50	$19.50
Purchase #7	$234.89	10.218%	$258.8911	$258.89	$258.90	$258.90
7 purchase totals =	$863.16		$942.0809	$942.08	$942.05	$942.10