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	$98.58	6.868%	$105.3505	$105.35	$105.35	$105.40
Purchase #2	$71.89	8.866%	$78.2638	$78.26	$78.25	$78.30
Purchase #3	$94.95	11.770%	$106.1256	$106.13	$106.15	$106.10
Purchase #4	$110.85	6.661%	$118.2337	$118.23	$118.25	$118.20
Purchase #5	$6.33	13.855%	$7.207	$7.21	$7.20	$7.20
Purchase #6	$49.28	12.579%	$55.4789	$55.48	$55.50	$55.50
Purchase #7	$21.87	3.617%	$22.661	$22.66	$22.65	$22.70
7 purchase totals =	$453.75		$493.3205	$493.32	$493.35	$493.40