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	$97.28	13.408%	$110.3233	$110.32	$110.30	$110.30
Purchase #2	$170.46	13.117%	$192.8192	$192.82	$192.80	$192.80
Purchase #3	$17.46	5.474%	$18.4158	$18.42	$18.40	$18.40
Purchase #4	$172.93	13.838%	$196.8601	$196.86	$196.85	$196.90
Purchase #5	$229.84	3.775%	$238.5165	$238.52	$238.50	$238.50
Purchase #6	$180.90	4.175%	$188.4526	$188.45	$188.45	$188.50
Purchase #7	$99.44	10.447%	$109.8285	$109.83	$109.85	$109.80
7 purchase totals =	$968.31		$1,055.2160	$1,055.22	$1,055.15	$1,055.20