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	$179.89	13.384%	$203.9665	$203.97	$203.95	$204.00
Purchase #2	$166.74	9.671%	$182.8654	$182.87	$182.85	$182.90
Purchase #3	$26.40	7.685%	$28.4288	$28.43	$28.45	$28.40
Purchase #4	$90.35	11.507%	$100.7466	$100.75	$100.75	$100.70
Purchase #5	$99.57	12.800%	$112.315	$112.32	$112.30	$112.30
Purchase #6	$135.44	11.338%	$150.7962	$150.80	$150.80	$150.80
Purchase #7	$244.40	4.397%	$255.1463	$255.15	$255.15	$255.10
7 purchase totals =	$942.79		$1,034.2648	$1,034.29	$1,034.25	$1,034.20