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	$33.93	7.501%	$36.4751	$36.48	$36.50	$36.50
Purchase #2	$196.82	3.830%	$204.3582	$204.36	$204.35	$204.40
Purchase #3	$35.88	3.504%	$37.1372	$37.14	$37.15	$37.10
Purchase #4	$188.76	8.257%	$204.3459	$204.35	$204.35	$204.30
Purchase #5	$29.95	7.687%	$32.2523	$32.25	$32.25	$32.30
Purchase #6	$92.70	12.365%	$104.1624	$104.16	$104.15	$104.20
Purchase #7	$33.74	11.273%	$37.5435	$37.54	$37.55	$37.50
7 purchase totals =	$611.78		$656.2746	$656.28	$656.30	$656.30