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	$168.90	13.315%	$191.389	$191.39	$191.40	$191.40
Purchase #2	$44.91	7.811%	$48.4179	$48.42	$48.40	$48.40
Purchase #3	$118.39	6.752%	$126.3837	$126.38	$126.40	$126.40
Purchase #4	$235.29	12.829%	$265.4754	$265.48	$265.50	$265.50
Purchase #5	$201.82	10.238%	$222.4823	$222.48	$222.50	$222.50
Purchase #6	$44.30	3.323%	$45.7721	$45.77	$45.75	$45.80
Purchase #7	$205.72	11.201%	$228.7627	$228.76	$228.75	$228.80
7 purchase totals =	$1,019.33		$1,128.6831	$1,128.68	$1,128.70	$1,128.80