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	$110.42	7.264%	$118.4409	$118.44	$118.45	$118.40
Purchase #2	$61.95	4.387%	$64.6677	$64.67	$64.65	$64.70
Purchase #3	$162.80	13.825%	$185.3071	$185.31	$185.30	$185.30
Purchase #4	$139.72	10.778%	$154.779	$154.78	$154.80	$154.80
Purchase #5	$173.60	11.755%	$194.0067	$194.01	$194.00	$194.00
Purchase #6	$218.50	11.809%	$244.3027	$244.30	$244.30	$244.30
Purchase #7	$185.83	13.679%	$211.2497	$211.25	$211.25	$211.20
7 purchase totals =	$1,052.82		$1,172.7538	$1,172.76	$1,172.75	$1,172.70