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	$86.35	10.190%	$95.1491	$95.15	$95.15	$95.10
Purchase #2	$98.52	13.475%	$111.7956	$111.80	$111.80	$111.80
Purchase #3	$91.69	8.126%	$99.1407	$99.14	$99.15	$99.10
Purchase #4	$45.31	9.553%	$49.6385	$49.64	$49.65	$49.60
Purchase #5	$164.48	13.134%	$186.0828	$186.08	$186.10	$186.10
Purchase #6	$130.56	9.605%	$143.1003	$143.10	$143.10	$143.10
Purchase #7	$209.34	3.280%	$216.2064	$216.21	$216.20	$216.20
7 purchase totals =	$826.25		$901.1134	$901.12	$901.15	$901.00