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	$232.77	4.530%	$243.3145	$243.31	$243.30	$243.30
Purchase #2	$70.91	8.496%	$76.9345	$76.93	$76.95	$76.90
Purchase #3	$38.26	13.808%	$43.5429	$43.54	$43.55	$43.50
Purchase #4	$188.39	3.107%	$194.2433	$194.24	$194.25	$194.20
Purchase #5	$125.34	8.612%	$136.1343	$136.13	$136.15	$136.10
Purchase #6	$121.62	4.801%	$127.459	$127.46	$127.45	$127.50
Purchase #7	$118.47	7.689%	$127.5792	$127.58	$127.60	$127.60
7 purchase totals =	$895.76		$949.2077	$949.19	$949.25	$949.10