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	$177.94	4.156%	$185.3352	$185.34	$185.35	$185.30
Purchase #2	$58.81	10.755%	$65.135	$65.14	$65.15	$65.10
Purchase #3	$86.54	12.568%	$97.4163	$97.42	$97.40	$97.40
Purchase #4	$130.30	12.398%	$146.4546	$146.45	$146.45	$146.50
Purchase #5	$20.54	9.440%	$22.479	$22.48	$22.50	$22.50
Purchase #6	$65.36	10.657%	$72.3254	$72.33	$72.35	$72.30
Purchase #7	$70.72	7.341%	$75.9116	$75.91	$75.90	$75.90
7 purchase totals =	$610.21		$665.0571	$665.07	$665.10	$665.00