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	$240.45	9.152%	$262.456	$262.46	$262.45	$262.50
Purchase #2	$72.73	7.786%	$78.3928	$78.39	$78.40	$78.40
Purchase #3	$245.53	5.188%	$258.2681	$258.27	$258.25	$258.30
Purchase #4	$164.73	3.526%	$170.5384	$170.54	$170.55	$170.50
Purchase #5	$148.66	6.769%	$158.7228	$158.72	$158.70	$158.70
Purchase #6	$25.85	11.378%	$28.7912	$28.79	$28.80	$28.80
Purchase #7	$10.56	5.596%	$11.1509	$11.15	$11.15	$11.20
7 purchase totals =	$908.51		$968.3202	$968.32	$968.30	$968.40