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	$88.74	3.604%	$91.9382	$91.94	$91.95	$91.90
Purchase #2	$49.87	3.290%	$51.5107	$51.51	$51.50	$51.50
Purchase #3	$144.96	4.122%	$150.9353	$150.94	$150.95	$150.90
Purchase #4	$202.61	11.465%	$225.8392	$225.84	$225.85	$225.80
Purchase #5	$213.37	11.773%	$238.4901	$238.49	$238.50	$238.50
Purchase #6	$204.71	3.329%	$211.5248	$211.52	$211.50	$211.50
Purchase #7	$237.29	9.245%	$259.2275	$259.23	$259.25	$259.20
7 purchase totals =	$1,141.55		$1,229.4658	$1,229.47	$1,229.50	$1,229.30