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	$113.85	11.662%	$127.1272	$127.13	$127.15	$127.10
Purchase #2	$203.67	12.489%	$229.1063	$229.11	$229.10	$229.10
Purchase #3	$57.44	4.230%	$59.8697	$59.87	$59.85	$59.90
Purchase #4	$126.30	5.360%	$133.0697	$133.07	$133.05	$133.10
Purchase #5	$109.89	7.287%	$117.8977	$117.90	$117.90	$117.90
Purchase #6	$226.60	6.298%	$240.8713	$240.87	$240.85	$240.90
Purchase #7	$180.32	11.869%	$201.7222	$201.72	$201.70	$201.70
7 purchase totals =	$1,018.07		$1,109.6641	$1,109.67	$1,109.60	$1,109.70