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	$96.97	8.610%	$105.3191	$105.32	$105.30	$105.30
Purchase #2	$137.32	11.217%	$152.7232	$152.72	$152.70	$152.70
Purchase #3	$183.47	9.515%	$200.9272	$200.93	$200.95	$200.90
Purchase #4	$83.53	6.629%	$89.0672	$89.07	$89.05	$89.10
Purchase #5	$88.40	6.415%	$94.0709	$94.07	$94.05	$94.10
Purchase #6	$19.87	11.288%	$22.1129	$22.11	$22.10	$22.10
Purchase #7	$88.84	11.444%	$99.0068	$99.01	$99.00	$99.00
7 purchase totals =	$698.40		$763.2273	$763.23	$763.15	$763.20