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	$55.73	7.372%	$59.8384	$59.84	$59.85	$59.80
Purchase #2	$77.32	6.505%	$82.3497	$82.35	$82.35	$82.30
Purchase #3	$85.33	4.490%	$89.1613	$89.16	$89.15	$89.20
Purchase #4	$195.66	4.456%	$204.3786	$204.38	$204.40	$204.40
Purchase #5	$237.55	4.155%	$247.4202	$247.42	$247.40	$247.40
Purchase #6	$222.79	13.845%	$253.6353	$253.64	$253.65	$253.60
Purchase #7	$115.78	3.130%	$119.4039	$119.40	$119.40	$119.40
7 purchase totals =	$990.16		$1,056.1874	$1,056.19	$1,056.20	$1,056.10