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	$228.68	10.872%	$253.5421	$253.54	$253.55	$253.50
Purchase #2	$7.74	13.152%	$8.758	$8.76	$8.75	$8.80
Purchase #3	$21.38	3.320%	$22.0898	$22.09	$22.10	$22.10
Purchase #4	$79.55	13.551%	$90.3298	$90.33	$90.35	$90.30
Purchase #5	$88.58	13.743%	$100.7535	$100.75	$100.75	$100.80
Purchase #6	$210.41	10.759%	$233.048	$233.05	$233.05	$233.00
Purchase #7	$98.92	11.118%	$109.9179	$109.92	$109.90	$109.90
7 purchase totals =	$735.26		$818.4391	$818.44	$818.45	$818.40