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	$32.83	3.210%	$33.8838	$33.88	$33.90	$33.90
Purchase #2	$213.75	5.104%	$224.6598	$224.66	$224.65	$224.70
Purchase #3	$116.30	9.510%	$127.3601	$127.36	$127.35	$127.40
Purchase #4	$38.28	11.663%	$42.7446	$42.74	$42.75	$42.70
Purchase #5	$167.25	9.379%	$182.9364	$182.94	$182.95	$182.90
Purchase #6	$101.82	4.636%	$106.5404	$106.54	$106.55	$106.50
Purchase #7	$203.80	9.498%	$223.1569	$223.16	$223.15	$223.20
7 purchase totals =	$874.03		$941.2820	$941.28	$941.30	$941.30