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	$166.41	3.374%	$172.0247	$172.02	$172.00	$172.00
Purchase #2	$200.27	6.459%	$213.2054	$213.21	$213.20	$213.20
Purchase #3	$93.55	6.130%	$99.2846	$99.28	$99.30	$99.30
Purchase #4	$91.33	9.763%	$100.2465	$100.25	$100.25	$100.20
Purchase #5	$177.61	9.296%	$194.1206	$194.12	$194.10	$194.10
Purchase #6	$84.38	6.718%	$90.0486	$90.05	$90.05	$90.00
Purchase #7	$222.68	12.660%	$250.8713	$250.87	$250.85	$250.90
7 purchase totals =	$1,036.23		$1,119.8017	$1,119.80	$1,119.75	$1,119.70