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	$195.78	4.734%	$205.0482	$205.05	$205.05	$205.00
Purchase #2	$168.59	11.730%	$188.3656	$188.37	$188.35	$188.40
Purchase #3	$89.72	11.461%	$100.0028	$100.00	$100.00	$100.00
Purchase #4	$12.55	6.840%	$13.4084	$13.41	$13.40	$13.40
Purchase #5	$150.46	9.846%	$165.2743	$165.27	$165.25	$165.30
Purchase #6	$141.31	6.267%	$150.1659	$150.17	$150.15	$150.20
Purchase #7	$62.90	7.814%	$67.815	$67.82	$67.80	$67.80
7 purchase totals =	$821.31		$890.0802	$890.09	$890.00	$890.10