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	$160.48	8.541%	$174.1866	$174.19	$174.20	$174.20
Purchase #2	$144.55	6.281%	$153.6292	$153.63	$153.65	$153.60
Purchase #3	$244.77	3.371%	$253.0212	$253.02	$253.00	$253.00
Purchase #4	$109.62	3.229%	$113.1596	$113.16	$113.15	$113.20
Purchase #5	$57.53	3.401%	$59.4866	$59.49	$59.50	$59.50
Purchase #6	$118.62	4.116%	$123.5024	$123.50	$123.50	$123.50
Purchase #7	$92.91	9.380%	$101.625	$101.63	$101.65	$101.60
7 purchase totals =	$928.48		$978.6106	$978.62	$978.65	$978.60