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	$161.82	13.289%	$183.3243	$183.32	$183.30	$183.30
Purchase #2	$35.44	5.282%	$37.3119	$37.31	$37.30	$37.30
Purchase #3	$138.69	10.118%	$152.7227	$152.72	$152.70	$152.70
Purchase #4	$198.41	11.811%	$221.8442	$221.84	$221.85	$221.80
Purchase #5	$229.52	3.315%	$237.1286	$237.13	$237.15	$237.10
Purchase #6	$50.41	8.154%	$54.5204	$54.52	$54.50	$54.50
Purchase #7	$129.41	8.277%	$140.1213	$140.12	$140.10	$140.10
7 purchase totals =	$943.70		$1,026.9734	$1,026.96	$1,026.90	$1,026.80