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	$248.53	10.373%	$274.31	$274.31	$274.30	$274.30
Purchase #2	$92.40	9.200%	$100.9008	$100.90	$100.90	$100.90
Purchase #3	$41.50	13.618%	$47.1515	$47.15	$47.15	$47.20
Purchase #4	$167.38	8.130%	$180.988	$180.99	$181.00	$181.00
Purchase #5	$40.50	3.758%	$42.022	$42.02	$42.00	$42.00
Purchase #6	$112.79	11.188%	$125.4089	$125.41	$125.40	$125.40
Purchase #7	$196.38	6.618%	$209.3764	$209.38	$209.40	$209.40
7 purchase totals =	$899.48		$980.1576	$980.16	$980.15	$980.20