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	$175.39	13.156%	$198.4643	$198.46	$198.45	$198.50
Purchase #2	$210.90	7.815%	$227.3818	$227.38	$227.40	$227.40
Purchase #3	$120.32	6.738%	$128.4272	$128.43	$128.45	$128.40
Purchase #4	$44.29	7.603%	$47.6574	$47.66	$47.65	$47.70
Purchase #5	$149.78	12.673%	$168.7616	$168.76	$168.75	$168.80
Purchase #6	$148.96	11.426%	$165.9802	$165.98	$166.00	$166.00
Purchase #7	$119.73	7.301%	$128.4715	$128.47	$128.45	$128.50
7 purchase totals =	$969.37		$1,065.1440	$1,065.14	$1,065.15	$1,065.30