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	$79.47	7.604%	$85.5129	$85.51	$85.50	$85.50
Purchase #2	$168.26	7.726%	$181.2598	$181.26	$181.25	$181.30
Purchase #3	$135.83	6.143%	$144.174	$144.17	$144.15	$144.20
Purchase #4	$240.53	4.481%	$251.3081	$251.31	$251.30	$251.30
Purchase #5	$211.56	10.421%	$233.6067	$233.61	$233.60	$233.60
Purchase #6	$57.90	9.234%	$63.2465	$63.25	$63.25	$63.20
Purchase #7	$168.40	13.385%	$190.9403	$190.94	$190.95	$190.90
7 purchase totals =	$1,061.95		$1,150.0483	$1,150.05	$1,150.00	$1,150.00