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	$48.30	4.842%	$50.6387	$50.64	$50.65	$50.60
Purchase #2	$221.27	12.214%	$248.2959	$248.30	$248.30	$248.30
Purchase #3	$43.67	9.833%	$47.9641	$47.96	$47.95	$48.00
Purchase #4	$83.99	6.253%	$89.2419	$89.24	$89.25	$89.20
Purchase #5	$42.87	5.589%	$45.266	$45.27	$45.25	$45.30
Purchase #6	$156.27	5.830%	$165.3805	$165.38	$165.40	$165.40
Purchase #7	$72.51	11.448%	$80.8109	$80.81	$80.80	$80.80
7 purchase totals =	$668.88		$727.5980	$727.60	$727.60	$727.60