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	$190.47	4.149%	$198.3726	$198.37	$198.35	$198.40
Purchase #2	$231.90	4.273%	$241.8091	$241.81	$241.80	$241.80
Purchase #3	$148.80	11.286%	$165.5936	$165.59	$165.60	$165.60
Purchase #4	$43.72	7.303%	$46.9129	$46.91	$46.90	$46.90
Purchase #5	$153.35	10.317%	$169.1711	$169.17	$169.15	$169.20
Purchase #6	$142.84	11.279%	$158.9509	$158.95	$158.95	$159.00
Purchase #7	$242.27	9.349%	$264.9198	$264.92	$264.90	$264.90
7 purchase totals =	$1,153.35		$1,245.7300	$1,245.72	$1,245.65	$1,245.80