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	$59.60	12.556%	$67.0834	$67.08	$67.10	$67.10
Purchase #2	$111.90	13.570%	$127.0848	$127.08	$127.10	$127.10
Purchase #3	$9.47	11.366%	$10.5464	$10.55	$10.55	$10.50
Purchase #4	$212.73	13.326%	$241.0784	$241.08	$241.10	$241.10
Purchase #5	$18.33	12.407%	$20.6042	$20.60	$20.60	$20.60
Purchase #6	$134.77	13.260%	$152.6405	$152.64	$152.65	$152.60
Purchase #7	$148.77	3.618%	$154.1525	$154.15	$154.15	$154.20
7 purchase totals =	$695.57		$773.1902	$773.18	$773.25	$773.20