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	$122.35	4.398%	$127.731	$127.73	$127.75	$127.70
Purchase #2	$86.30	9.318%	$94.3414	$94.34	$94.35	$94.30
Purchase #3	$156.38	5.872%	$165.5626	$165.56	$165.55	$165.60
Purchase #4	$245.69	8.200%	$265.8366	$265.84	$265.85	$265.80
Purchase #5	$157.59	13.404%	$178.7134	$178.71	$178.70	$178.70
Purchase #6	$173.47	4.836%	$181.859	$181.86	$181.85	$181.90
Purchase #7	$65.33	8.231%	$70.7073	$70.71	$70.70	$70.70
7 purchase totals =	$1,007.11		$1,084.7513	$1,084.75	$1,084.75	$1,084.70