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	$174.53	9.867%	$191.7509	$191.75	$191.75	$191.80
Purchase #2	$162.64	4.601%	$170.1231	$170.12	$170.10	$170.10
Purchase #3	$91.90	6.744%	$98.0977	$98.10	$98.10	$98.10
Purchase #4	$208.91	3.799%	$216.8465	$216.85	$216.85	$216.80
Purchase #5	$148.27	7.544%	$159.4555	$159.46	$159.45	$159.50
Purchase #6	$71.78	13.220%	$81.2693	$81.27	$81.25	$81.30
Purchase #7	$137.39	4.196%	$143.1549	$143.15	$143.15	$143.20
7 purchase totals =	$995.42		$1,060.6979	$1,060.70	$1,060.65	$1,060.80