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	$33.50	12.157%	$37.5726	$37.57	$37.55	$37.60
Purchase #2	$82.31	13.138%	$93.1239	$93.12	$93.10	$93.10
Purchase #3	$155.49	5.587%	$164.1772	$164.18	$164.20	$164.20
Purchase #4	$92.28	7.598%	$99.2914	$99.29	$99.30	$99.30
Purchase #5	$217.58	6.376%	$231.4529	$231.45	$231.45	$231.50
Purchase #6	$185.74	13.184%	$210.228	$210.23	$210.25	$210.20
Purchase #7	$171.36	6.471%	$182.4487	$182.45	$182.45	$182.40
7 purchase totals =	$938.26		$1,018.2947	$1,018.29	$1,018.30	$1,018.30