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	$109.87	3.188%	$113.3727	$113.37	$113.35	$113.40
Purchase #2	$88.82	8.762%	$96.6024	$96.60	$96.60	$96.60
Purchase #3	$89.30	7.219%	$95.7466	$95.75	$95.75	$95.70
Purchase #4	$47.83	10.417%	$52.8125	$52.81	$52.80	$52.80
Purchase #5	$93.97	4.330%	$98.0389	$98.04	$98.05	$98.00
Purchase #6	$43.41	12.480%	$48.8276	$48.83	$48.85	$48.80
Purchase #7	$59.31	4.816%	$62.1664	$62.17	$62.15	$62.20
7 purchase totals =	$532.51		$567.5671	$567.57	$567.55	$567.50