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	$137.25	4.637%	$143.6143	$143.61	$143.60	$143.60
Purchase #2	$57.88	3.167%	$59.7131	$59.71	$59.70	$59.70
Purchase #3	$48.38	11.278%	$53.8363	$53.84	$53.85	$53.80
Purchase #4	$149.27	11.764%	$166.8301	$166.83	$166.85	$166.80
Purchase #5	$210.47	10.658%	$232.9019	$232.90	$232.90	$232.90
Purchase #6	$158.83	4.133%	$165.3944	$165.39	$165.40	$165.40
Purchase #7	$221.62	10.551%	$245.0031	$245.00	$245.00	$245.00
7 purchase totals =	$983.70		$1,067.2932	$1,067.28	$1,067.30	$1,067.20