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	$165.42	3.117%	$170.5761	$170.58	$170.60	$170.60
Purchase #2	$120.80	5.454%	$127.3884	$127.39	$127.40	$127.40
Purchase #3	$58.41	10.870%	$64.7592	$64.76	$64.75	$64.80
Purchase #4	$210.90	5.220%	$221.909	$221.91	$221.90	$221.90
Purchase #5	$162.96	3.287%	$168.3165	$168.32	$168.30	$168.30
Purchase #6	$229.28	9.349%	$250.7154	$250.72	$250.70	$250.70
Purchase #7	$230.41	9.731%	$252.8312	$252.83	$252.85	$252.80
7 purchase totals =	$1,178.18		$1,256.4958	$1,256.51	$1,256.50	$1,256.50