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	$107.49	3.385%	$111.1285	$111.13	$111.15	$111.10
Purchase #2	$46.94	8.399%	$50.8825	$50.88	$50.90	$50.90
Purchase #3	$156.58	11.485%	$174.5632	$174.56	$174.55	$174.60
Purchase #4	$54.59	8.261%	$59.0997	$59.10	$59.10	$59.10
Purchase #5	$198.78	12.301%	$223.2319	$223.23	$223.25	$223.20
Purchase #6	$35.55	4.322%	$37.0865	$37.09	$37.10	$37.10
Purchase #7	$49.78	9.270%	$54.3946	$54.39	$54.40	$54.40
7 purchase totals =	$649.71		$710.3869	$710.38	$710.45	$710.40