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	$160.91	5.114%	$169.1389	$169.14	$169.15	$169.10
Purchase #2	$139.94	7.586%	$150.5558	$150.56	$150.55	$150.60
Purchase #3	$125.48	3.599%	$129.996	$130.00	$130.00	$130.00
Purchase #4	$96.56	13.117%	$109.2258	$109.23	$109.25	$109.20
Purchase #5	$152.37	6.196%	$161.8108	$161.81	$161.80	$161.80
Purchase #6	$12.33	10.540%	$13.6296	$13.63	$13.65	$13.60
Purchase #7	$102.88	13.428%	$116.6947	$116.69	$116.70	$116.70
7 purchase totals =	$790.47		$851.0516	$851.06	$851.10	$851.00