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	$103.91	6.180%	$110.3316	$110.33	$110.35	$110.30
Purchase #2	$9.50	9.766%	$10.4278	$10.43	$10.45	$10.40
Purchase #3	$52.70	6.503%	$56.1271	$56.13	$56.15	$56.10
Purchase #4	$81.87	9.573%	$89.7074	$89.71	$89.70	$89.70
Purchase #5	$44.62	13.311%	$50.5594	$50.56	$50.55	$50.60
Purchase #6	$109.98	12.215%	$123.4141	$123.41	$123.40	$123.40
Purchase #7	$80.83	6.361%	$85.9716	$85.97	$85.95	$86.00
7 purchase totals =	$483.41		$526.5390	$526.54	$526.55	$526.50