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	$101.81	7.513%	$109.459	$109.46	$109.45	$109.50
Purchase #2	$84.61	5.809%	$89.525	$89.53	$89.55	$89.50
Purchase #3	$83.74	8.810%	$91.1175	$91.12	$91.10	$91.10
Purchase #4	$79.36	10.493%	$87.6872	$87.69	$87.70	$87.70
Purchase #5	$209.91	5.343%	$221.1255	$221.13	$221.15	$221.10
Purchase #6	$31.48	12.753%	$35.4946	$35.49	$35.50	$35.50
Purchase #7	$240.86	13.834%	$274.1806	$274.18	$274.20	$274.20
7 purchase totals =	$831.77		$908.5894	$908.60	$908.65	$908.60