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	$185.66	7.142%	$198.9198	$198.92	$198.90	$198.90
Purchase #2	$65.53	11.287%	$72.9264	$72.93	$72.95	$72.90
Purchase #3	$26.28	7.515%	$28.2549	$28.25	$28.25	$28.30
Purchase #4	$9.62	11.424%	$10.719	$10.72	$10.70	$10.70
Purchase #5	$164.78	4.361%	$171.9661	$171.97	$171.95	$172.00
Purchase #6	$35.80	11.427%	$39.8909	$39.89	$39.90	$39.90
Purchase #7	$92.54	13.370%	$104.9126	$104.91	$104.90	$104.90
7 purchase totals =	$580.21		$627.5897	$627.59	$627.55	$627.60