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	$93.27	13.235%	$105.6143	$105.61	$105.60	$105.60
Purchase #2	$93.41	3.268%	$96.4626	$96.46	$96.45	$96.50
Purchase #3	$52.55	9.388%	$57.4834	$57.48	$57.50	$57.50
Purchase #4	$130.72	5.104%	$137.3919	$137.39	$137.40	$137.40
Purchase #5	$41.81	7.762%	$45.0553	$45.06	$45.05	$45.10
Purchase #6	$239.25	9.135%	$261.1055	$261.11	$261.10	$261.10
Purchase #7	$42.33	4.345%	$44.1692	$44.17	$44.15	$44.20
7 purchase totals =	$693.34		$747.2822	$747.28	$747.25	$747.40