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	$49.90	5.328%	$52.5587	$52.56	$52.55	$52.60
Purchase #2	$25.25	11.616%	$28.183	$28.18	$28.20	$28.20
Purchase #3	$229.96	5.503%	$242.6147	$242.61	$242.60	$242.60
Purchase #4	$120.95	6.260%	$128.5215	$128.52	$128.50	$128.50
Purchase #5	$32.42	3.285%	$33.485	$33.49	$33.50	$33.50
Purchase #6	$109.52	4.319%	$114.2502	$114.25	$114.25	$114.30
Purchase #7	$182.35	4.528%	$190.6068	$190.61	$190.60	$190.60
7 purchase totals =	$750.35		$790.2199	$790.22	$790.20	$790.30