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	$250.74	6.807%	$267.8079	$267.81	$267.80	$267.80
Purchase #2	$141.37	13.299%	$160.1708	$160.17	$160.15	$160.20
Purchase #3	$7.60	3.172%	$7.8411	$7.84	$7.85	$7.80
Purchase #4	$151.32	11.558%	$168.8096	$168.81	$168.80	$168.80
Purchase #5	$199.79	11.842%	$223.4491	$223.45	$223.45	$223.40
Purchase #6	$59.88	4.528%	$62.5914	$62.59	$62.60	$62.60
Purchase #7	$139.60	6.186%	$148.2357	$148.24	$148.25	$148.20
7 purchase totals =	$950.30		$1,038.9056	$1,038.91	$1,038.90	$1,038.80