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	$174.33	8.770%	$189.6187	$189.62	$189.60	$189.60
Purchase #2	$219.61	11.241%	$244.2964	$244.30	$244.30	$244.30
Purchase #3	$230.44	10.436%	$254.4887	$254.49	$254.50	$254.50
Purchase #4	$65.69	4.153%	$68.4181	$68.42	$68.40	$68.40
Purchase #5	$78.53	5.602%	$82.9293	$82.93	$82.95	$82.90
Purchase #6	$148.47	5.227%	$156.2305	$156.23	$156.25	$156.20
Purchase #7	$62.98	3.764%	$65.3506	$65.35	$65.35	$65.40
7 purchase totals =	$980.05		$1,061.3323	$1,061.34	$1,061.35	$1,061.30