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	$103.72	12.607%	$116.796	$116.80	$116.80	$116.80
Purchase #2	$84.60	12.537%	$95.2063	$95.21	$95.20	$95.20
Purchase #3	$110.85	11.198%	$123.263	$123.26	$123.25	$123.30
Purchase #4	$42.71	8.520%	$46.3489	$46.35	$46.35	$46.30
Purchase #5	$92.68	6.441%	$98.6495	$98.65	$98.65	$98.60
Purchase #6	$245.43	12.254%	$275.505	$275.51	$275.50	$275.50
Purchase #7	$250.33	5.331%	$263.6751	$263.68	$263.70	$263.70
7 purchase totals =	$930.32		$1,019.4438	$1,019.46	$1,019.45	$1,019.40