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	$203.44	9.751%	$223.2774	$223.28	$223.30	$223.30
Purchase #2	$244.50	13.218%	$276.818	$276.82	$276.80	$276.80
Purchase #3	$171.48	11.479%	$191.1642	$191.16	$191.15	$191.20
Purchase #4	$158.98	3.257%	$164.158	$164.16	$164.15	$164.20
Purchase #5	$88.55	6.541%	$94.3421	$94.34	$94.35	$94.30
Purchase #6	$210.29	11.175%	$233.7899	$233.79	$233.80	$233.80
Purchase #7	$237.31	9.116%	$258.9432	$258.94	$258.95	$258.90
7 purchase totals =	$1,314.55		$1,442.4928	$1,442.49	$1,442.50	$1,442.50