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	$137.77	7.655%	$148.3163	$148.32	$148.30	$148.30
Purchase #2	$176.80	13.588%	$200.8236	$200.82	$200.80	$200.80
Purchase #3	$92.68	11.356%	$103.2047	$103.20	$103.20	$103.20
Purchase #4	$30.56	5.397%	$32.2093	$32.21	$32.20	$32.20
Purchase #5	$128.44	11.592%	$143.3288	$143.33	$143.35	$143.30
Purchase #6	$250.90	4.614%	$262.4765	$262.48	$262.50	$262.50
Purchase #7	$118.31	6.362%	$125.8369	$125.84	$125.85	$125.80
7 purchase totals =	$935.46		$1,016.1961	$1,016.20	$1,016.20	$1,016.10