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	$183.56	3.701%	$190.3536	$190.35	$190.35	$190.40
Purchase #2	$99.59	10.429%	$109.9762	$109.98	$110.00	$110.00
Purchase #3	$81.33	4.758%	$85.1997	$85.20	$85.20	$85.20
Purchase #4	$152.54	4.470%	$159.3585	$159.36	$159.35	$159.40
Purchase #5	$99.53	12.163%	$111.6358	$111.64	$111.65	$111.60
Purchase #6	$82.50	5.807%	$87.2908	$87.29	$87.30	$87.30
Purchase #7	$32.54	11.408%	$36.2522	$36.25	$36.25	$36.30
7 purchase totals =	$731.59		$780.0668	$780.07	$780.10	$780.20