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	$99.96	12.589%	$112.544	$112.54	$112.55	$112.50
Purchase #2	$189.48	13.773%	$215.5771	$215.58	$215.60	$215.60
Purchase #3	$39.47	10.594%	$43.6515	$43.65	$43.65	$43.70
Purchase #4	$248.70	7.596%	$267.5913	$267.59	$267.60	$267.60
Purchase #5	$126.62	4.609%	$132.4559	$132.46	$132.45	$132.50
Purchase #6	$55.81	6.221%	$59.2819	$59.28	$59.30	$59.30
Purchase #7	$188.45	13.700%	$214.2677	$214.27	$214.25	$214.30
7 purchase totals =	$948.49		$1,045.3694	$1,045.37	$1,045.40	$1,045.50