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	$179.30	4.516%	$187.3972	$187.40	$187.40	$187.40
Purchase #2	$233.41	10.795%	$258.6066	$258.61	$258.60	$258.60
Purchase #3	$223.72	3.849%	$232.331	$232.33	$232.35	$232.30
Purchase #4	$167.74	10.773%	$185.8106	$185.81	$185.80	$185.80
Purchase #5	$152.77	4.420%	$159.5224	$159.52	$159.50	$159.50
Purchase #6	$37.95	6.805%	$40.5325	$40.53	$40.55	$40.50
Purchase #7	$180.65	9.629%	$198.0448	$198.04	$198.05	$198.00
7 purchase totals =	$1,175.54		$1,262.2451	$1,262.24	$1,262.25	$1,262.10