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	$113.79	12.412%	$127.9136	$127.91	$127.90	$127.90
Purchase #2	$241.53	8.130%	$261.1664	$261.17	$261.15	$261.20
Purchase #3	$14.64	3.225%	$15.1121	$15.11	$15.10	$15.10
Purchase #4	$59.50	5.437%	$62.735	$62.74	$62.75	$62.70
Purchase #5	$239.44	4.550%	$250.3345	$250.33	$250.35	$250.30
Purchase #6	$229.51	12.333%	$257.8155	$257.82	$257.80	$257.80
Purchase #7	$36.78	13.708%	$41.8218	$41.82	$41.80	$41.80
7 purchase totals =	$935.19		$1,016.8989	$1,016.90	$1,016.85	$1,016.80