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	$152.53	6.778%	$162.8685	$162.87	$162.85	$162.90
Purchase #2	$97.52	9.305%	$106.5942	$106.59	$106.60	$106.60
Purchase #3	$242.96	11.341%	$270.5141	$270.51	$270.50	$270.50
Purchase #4	$20.63	8.218%	$22.3254	$22.33	$22.35	$22.30
Purchase #5	$171.31	4.323%	$178.7157	$178.72	$178.70	$178.70
Purchase #6	$215.89	10.580%	$238.7312	$238.73	$238.75	$238.70
Purchase #7	$57.54	12.240%	$64.5829	$64.58	$64.60	$64.60
7 purchase totals =	$958.38		$1,044.3320	$1,044.33	$1,044.35	$1,044.30