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	$25.31	8.653%	$27.5001	$27.50	$27.50	$27.50
Purchase #2	$5.49	5.584%	$5.7966	$5.80	$5.80	$5.80
Purchase #3	$100.39	3.507%	$103.9107	$103.91	$103.90	$103.90
Purchase #4	$154.54	11.638%	$172.5254	$172.53	$172.55	$172.50
Purchase #5	$110.77	3.154%	$114.2637	$114.26	$114.25	$114.30
Purchase #6	$183.51	12.501%	$206.4506	$206.45	$206.45	$206.50
Purchase #7	$75.41	10.483%	$83.3152	$83.32	$83.30	$83.30
7 purchase totals =	$655.42		$713.7623	$713.77	$713.75	$713.80