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	$249.47	5.753%	$263.822	$263.82	$263.80	$263.80
Purchase #2	$70.55	3.213%	$72.8168	$72.82	$72.80	$72.80
Purchase #3	$42.99	11.799%	$48.0624	$48.06	$48.05	$48.10
Purchase #4	$31.73	4.483%	$33.1525	$33.15	$33.15	$33.20
Purchase #5	$48.61	9.310%	$53.1356	$53.14	$53.15	$53.10
Purchase #6	$181.47	12.564%	$204.2699	$204.27	$204.25	$204.30
Purchase #7	$140.67	13.111%	$159.1132	$159.11	$159.10	$159.10
7 purchase totals =	$765.49		$834.3724	$834.37	$834.30	$834.40