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	$226.44	12.769%	$255.3541	$255.35	$255.35	$255.40
Purchase #2	$240.46	8.507%	$260.9159	$260.92	$260.90	$260.90
Purchase #3	$49.38	3.589%	$51.1522	$51.15	$51.15	$51.20
Purchase #4	$55.38	3.501%	$57.3189	$57.32	$57.30	$57.30
Purchase #5	$94.64	12.242%	$106.2258	$106.23	$106.25	$106.20
Purchase #6	$240.32	8.103%	$259.7931	$259.79	$259.80	$259.80
Purchase #7	$90.56	4.292%	$94.4468	$94.45	$94.45	$94.40
7 purchase totals =	$997.18		$1,085.2068	$1,085.21	$1,085.20	$1,085.20