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	$242.75	4.369%	$253.3557	$253.36	$253.35	$253.40
Purchase #2	$250.73	5.688%	$264.9915	$264.99	$265.00	$265.00
Purchase #3	$230.67	8.860%	$251.1074	$251.11	$251.10	$251.10
Purchase #4	$54.51	8.460%	$59.1215	$59.12	$59.10	$59.10
Purchase #5	$158.56	5.567%	$167.387	$167.39	$167.40	$167.40
Purchase #6	$39.35	8.502%	$42.6955	$42.70	$42.70	$42.70
Purchase #7	$65.91	9.625%	$72.2538	$72.25	$72.25	$72.30
7 purchase totals =	$1,042.48		$1,110.9124	$1,110.92	$1,110.90	$1,111.00