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	$134.41	11.858%	$150.3483	$150.35	$150.35	$150.30
Purchase #2	$186.42	5.579%	$196.8204	$196.82	$196.80	$196.80
Purchase #3	$237.36	5.385%	$250.1418	$250.14	$250.15	$250.10
Purchase #4	$96.81	6.510%	$103.1123	$103.11	$103.10	$103.10
Purchase #5	$109.92	12.123%	$123.2456	$123.25	$123.25	$123.20
Purchase #6	$42.53	13.199%	$48.1435	$48.14	$48.15	$48.10
Purchase #7	$93.43	3.639%	$96.8299	$96.83	$96.85	$96.80
7 purchase totals =	$900.88		$968.6418	$968.64	$968.65	$968.40