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	$174.82	8.847%	$190.2863	$190.29	$190.30	$190.30
Purchase #2	$120.52	6.780%	$128.6913	$128.69	$128.70	$128.70
Purchase #3	$168.93	7.561%	$181.7028	$181.70	$181.70	$181.70
Purchase #4	$55.42	7.618%	$59.6419	$59.64	$59.65	$59.60
Purchase #5	$39.36	7.365%	$42.2589	$42.26	$42.25	$42.30
Purchase #6	$100.85	3.657%	$104.5381	$104.54	$104.55	$104.50
Purchase #7	$60.95	13.871%	$69.4044	$69.40	$69.40	$69.40
7 purchase totals =	$720.85		$776.5237	$776.52	$776.55	$776.50