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	$92.77	13.869%	$105.6363	$105.64	$105.65	$105.60
Purchase #2	$244.69	4.319%	$255.2582	$255.26	$255.25	$255.30
Purchase #3	$145.83	11.622%	$162.7784	$162.78	$162.80	$162.80
Purchase #4	$99.71	11.172%	$110.8496	$110.85	$110.85	$110.80
Purchase #5	$219.51	8.566%	$238.3132	$238.31	$238.30	$238.30
Purchase #6	$142.51	8.847%	$155.1179	$155.12	$155.10	$155.10
Purchase #7	$40.46	4.737%	$42.3766	$42.38	$42.40	$42.40
7 purchase totals =	$985.48		$1,070.3302	$1,070.34	$1,070.35	$1,070.30