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	$236.46	5.238%	$248.8458	$248.85	$248.85	$248.80
Purchase #2	$211.94	12.485%	$238.4007	$238.40	$238.40	$238.40
Purchase #3	$41.32	8.496%	$44.8305	$44.83	$44.85	$44.80
Purchase #4	$150.95	11.824%	$168.7983	$168.80	$168.80	$168.80
Purchase #5	$239.99	9.690%	$263.245	$263.25	$263.25	$263.20
Purchase #6	$83.73	8.473%	$90.8244	$90.82	$90.80	$90.80
Purchase #7	$191.43	9.868%	$210.3203	$210.32	$210.30	$210.30
7 purchase totals =	$1,155.82		$1,265.2650	$1,265.27	$1,265.25	$1,265.10