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	$236.49	7.698%	$254.695	$254.70	$254.70	$254.70
Purchase #2	$150.56	6.205%	$159.9022	$159.90	$159.90	$159.90
Purchase #3	$128.49	5.301%	$135.3013	$135.30	$135.30	$135.30
Purchase #4	$60.33	10.287%	$66.5361	$66.54	$66.55	$66.50
Purchase #5	$79.37	12.344%	$89.1674	$89.17	$89.15	$89.20
Purchase #6	$160.57	4.832%	$168.3287	$168.33	$168.35	$168.30
Purchase #7	$250.73	9.191%	$273.7746	$273.77	$273.75	$273.80
7 purchase totals =	$1,066.54		$1,147.7053	$1,147.71	$1,147.70	$1,147.70