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	$109.67	3.281%	$113.2683	$113.27	$113.25	$113.30
Purchase #2	$90.34	11.459%	$100.6921	$100.69	$100.70	$100.70
Purchase #3	$112.50	12.160%	$126.18	$126.18	$126.20	$126.20
Purchase #4	$194.88	5.122%	$204.8618	$204.86	$204.85	$204.90
Purchase #5	$34.72	5.543%	$36.6445	$36.64	$36.65	$36.60
Purchase #6	$242.33	13.764%	$275.6843	$275.68	$275.70	$275.70
Purchase #7	$129.46	11.311%	$144.1032	$144.10	$144.10	$144.10
7 purchase totals =	$913.90		$1,001.4342	$1,001.42	$1,001.45	$1,001.50