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	$94.91	4.507%	$99.1876	$99.19	$99.20	$99.20
Purchase #2	$152.25	6.594%	$162.2894	$162.29	$162.30	$162.30
Purchase #3	$148.66	7.540%	$159.869	$159.87	$159.85	$159.90
Purchase #4	$145.25	7.573%	$156.2498	$156.25	$156.25	$156.20
Purchase #5	$156.90	3.455%	$162.3209	$162.32	$162.30	$162.30
Purchase #6	$17.52	4.683%	$18.3405	$18.34	$18.35	$18.30
Purchase #7	$67.37	6.240%	$71.5739	$71.57	$71.55	$71.60
7 purchase totals =	$782.86		$829.8311	$829.83	$829.80	$829.80