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	$43.53	10.582%	$48.1363	$48.14	$48.15	$48.10
Purchase #2	$147.95	5.612%	$156.253	$156.25	$156.25	$156.30
Purchase #3	$167.90	10.123%	$184.8965	$184.90	$184.90	$184.90
Purchase #4	$108.44	4.140%	$112.9294	$112.93	$112.95	$112.90
Purchase #5	$57.39	4.349%	$59.8859	$59.89	$59.90	$59.90
Purchase #6	$165.77	8.298%	$179.5256	$179.53	$179.55	$179.50
Purchase #7	$99.72	5.527%	$105.2315	$105.23	$105.25	$105.20
7 purchase totals =	$790.70		$846.8582	$846.87	$846.95	$846.80