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	$71.34	4.479%	$74.5353	$74.54	$74.55	$74.50
Purchase #2	$192.56	6.113%	$204.3312	$204.33	$204.35	$204.30
Purchase #3	$240.67	8.668%	$261.5313	$261.53	$261.55	$261.50
Purchase #4	$188.63	11.501%	$210.3243	$210.32	$210.30	$210.30
Purchase #5	$89.31	10.592%	$98.7697	$98.77	$98.75	$98.80
Purchase #6	$155.36	12.236%	$174.3698	$174.37	$174.35	$174.40
Purchase #7	$34.47	7.793%	$37.1562	$37.16	$37.15	$37.20
7 purchase totals =	$972.34		$1,061.0178	$1,061.02	$1,061.00	$1,061.00