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	$99.50	10.438%	$109.8858	$109.89	$109.90	$109.90
Purchase #2	$96.56	9.470%	$105.7042	$105.70	$105.70	$105.70
Purchase #3	$116.40	9.386%	$127.3253	$127.33	$127.35	$127.30
Purchase #4	$131.27	6.257%	$139.4836	$139.48	$139.50	$139.50
Purchase #5	$226.36	3.415%	$234.0902	$234.09	$234.10	$234.10
Purchase #6	$249.31	5.427%	$262.8401	$262.84	$262.85	$262.80
Purchase #7	$158.40	8.599%	$172.0208	$172.02	$172.00	$172.00
7 purchase totals =	$1,077.80		$1,151.3500	$1,151.35	$1,151.40	$1,151.30