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	$119.49	7.744%	$128.7433	$128.74	$128.75	$128.70
Purchase #2	$79.43	12.488%	$89.3492	$89.35	$89.35	$89.30
Purchase #3	$180.93	13.732%	$205.7753	$205.78	$205.80	$205.80
Purchase #4	$204.28	11.723%	$228.2277	$228.23	$228.25	$228.20
Purchase #5	$222.54	7.737%	$239.7579	$239.76	$239.75	$239.80
Purchase #6	$149.86	11.401%	$166.9455	$166.95	$166.95	$166.90
Purchase #7	$101.93	7.581%	$109.6573	$109.66	$109.65	$109.70
7 purchase totals =	$1,058.46		$1,168.4562	$1,168.47	$1,168.50	$1,168.40