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	$78.33	13.775%	$89.12	$89.12	$89.10	$89.10
Purchase #2	$166.47	7.460%	$178.8887	$178.89	$178.90	$178.90
Purchase #3	$215.58	12.643%	$242.8358	$242.84	$242.85	$242.80
Purchase #4	$112.48	10.204%	$123.9575	$123.96	$123.95	$124.00
Purchase #5	$98.54	11.161%	$109.538	$109.54	$109.55	$109.50
Purchase #6	$160.75	11.277%	$178.8778	$178.88	$178.90	$178.90
Purchase #7	$96.30	4.796%	$100.9185	$100.92	$100.90	$100.90
7 purchase totals =	$928.45		$1,024.1363	$1,024.15	$1,024.15	$1,024.10