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	$36.36	13.678%	$41.3333	$41.33	$41.35	$41.30
Purchase #2	$197.47	9.336%	$215.9058	$215.91	$215.90	$215.90
Purchase #3	$30.97	11.543%	$34.5449	$34.54	$34.55	$34.50
Purchase #4	$29.55	8.728%	$32.1291	$32.13	$32.15	$32.10
Purchase #5	$196.41	13.626%	$223.1728	$223.17	$223.15	$223.20
Purchase #6	$25.96	11.146%	$28.8535	$28.85	$28.85	$28.90
Purchase #7	$91.48	10.651%	$101.2235	$101.22	$101.20	$101.20
7 purchase totals =	$608.20		$677.1629	$677.15	$677.15	$677.10