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	$149.27	9.161%	$162.9446	$162.94	$162.95	$162.90
Purchase #2	$138.51	6.608%	$147.6627	$147.66	$147.65	$147.70
Purchase #3	$166.86	11.424%	$185.9221	$185.92	$185.90	$185.90
Purchase #4	$62.89	7.499%	$67.6061	$67.61	$67.60	$67.60
Purchase #5	$239.32	12.733%	$269.7926	$269.79	$269.80	$269.80
Purchase #6	$131.74	8.283%	$142.652	$142.65	$142.65	$142.70
Purchase #7	$113.35	6.360%	$120.5591	$120.56	$120.55	$120.60
7 purchase totals =	$1,001.94		$1,097.1392	$1,097.13	$1,097.10	$1,097.20