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	$144.39	8.135%	$156.1361	$156.14	$156.15	$156.10
Purchase #2	$181.71	12.584%	$204.5764	$204.58	$204.60	$204.60
Purchase #3	$176.55	13.557%	$200.4849	$200.48	$200.50	$200.50
Purchase #4	$67.26	5.592%	$71.0212	$71.02	$71.00	$71.00
Purchase #5	$161.39	12.133%	$180.9714	$180.97	$180.95	$181.00
Purchase #6	$77.71	7.755%	$83.7364	$83.74	$83.75	$83.70
Purchase #7	$117.59	8.253%	$127.2947	$127.29	$127.30	$127.30
7 purchase totals =	$926.60		$1,024.2211	$1,024.22	$1,024.25	$1,024.20