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	$65.79	5.274%	$69.2598	$69.26	$69.25	$69.30
Purchase #2	$69.42	13.607%	$78.866	$78.87	$78.85	$78.90
Purchase #3	$58.52	7.371%	$62.8335	$62.83	$62.85	$62.80
Purchase #4	$146.43	6.376%	$155.7664	$155.77	$155.75	$155.80
Purchase #5	$36.37	11.150%	$40.4253	$40.43	$40.45	$40.40
Purchase #6	$249.33	3.164%	$257.2188	$257.22	$257.20	$257.20
Purchase #7	$39.45	9.843%	$43.3331	$43.33	$43.35	$43.30
7 purchase totals =	$665.31		$707.7029	$707.71	$707.70	$707.70