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	$97.35	12.716%	$109.729	$109.73	$109.75	$109.70
Purchase #2	$78.68	6.279%	$83.6203	$83.62	$83.60	$83.60
Purchase #3	$69.92	3.297%	$72.2253	$72.23	$72.25	$72.20
Purchase #4	$30.82	7.635%	$33.1731	$33.17	$33.15	$33.20
Purchase #5	$156.56	10.668%	$173.2618	$173.26	$173.25	$173.30
Purchase #6	$102.77	13.596%	$116.7426	$116.74	$116.75	$116.70
Purchase #7	$137.83	10.541%	$152.3587	$152.36	$152.35	$152.40
7 purchase totals =	$673.93		$741.1108	$741.11	$741.10	$741.10