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	$214.60	4.536%	$224.3343	$224.33	$224.35	$224.30
Purchase #2	$81.27	12.565%	$91.4816	$91.48	$91.50	$91.50
Purchase #3	$199.34	5.705%	$210.7123	$210.71	$210.70	$210.70
Purchase #4	$191.57	6.808%	$204.6121	$204.61	$204.60	$204.60
Purchase #5	$210.49	6.811%	$224.8265	$224.83	$224.85	$224.80
Purchase #6	$37.98	11.444%	$42.3264	$42.33	$42.35	$42.30
Purchase #7	$68.62	12.394%	$77.1248	$77.12	$77.10	$77.10
7 purchase totals =	$1,003.87		$1,075.4180	$1,075.41	$1,075.45	$1,075.30