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	$210.43	6.146%	$223.363	$223.36	$223.35	$223.40
Purchase #2	$38.66	10.312%	$42.6466	$42.65	$42.65	$42.60
Purchase #3	$18.98	9.840%	$20.8476	$20.85	$20.85	$20.80
Purchase #4	$33.83	11.463%	$37.7079	$37.71	$37.70	$37.70
Purchase #5	$165.49	5.396%	$174.4198	$174.42	$174.40	$174.40
Purchase #6	$6.95	3.367%	$7.184	$7.18	$7.20	$7.20
Purchase #7	$141.36	11.116%	$157.0736	$157.07	$157.05	$157.10
7 purchase totals =	$615.70		$663.2425	$663.24	$663.20	$663.20