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	$234.97	3.353%	$242.8485	$242.85	$242.85	$242.80
Purchase #2	$34.72	7.638%	$37.3719	$37.37	$37.35	$37.40
Purchase #3	$218.89	5.393%	$230.6947	$230.69	$230.70	$230.70
Purchase #4	$109.70	10.712%	$121.4511	$121.45	$121.45	$121.50
Purchase #5	$155.87	8.177%	$168.6155	$168.62	$168.60	$168.60
Purchase #6	$249.49	11.251%	$277.5601	$277.56	$277.55	$277.60
Purchase #7	$30.75	6.871%	$32.8628	$32.86	$32.85	$32.90
7 purchase totals =	$1,034.39		$1,111.4046	$1,111.40	$1,111.35	$1,111.50