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	$177.36	9.555%	$194.3067	$194.31	$194.30	$194.30
Purchase #2	$57.33	7.589%	$61.6808	$61.68	$61.70	$61.70
Purchase #3	$222.91	4.594%	$233.1505	$233.15	$233.15	$233.20
Purchase #4	$165.98	12.585%	$186.8686	$186.87	$186.85	$186.90
Purchase #5	$18.60	9.770%	$20.4172	$20.42	$20.40	$20.40
Purchase #6	$238.59	7.261%	$255.914	$255.91	$255.90	$255.90
Purchase #7	$187.99	5.632%	$198.5776	$198.58	$198.60	$198.60
7 purchase totals =	$1,068.76		$1,150.9154	$1,150.92	$1,150.90	$1,151.00