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	$148.89	3.462%	$154.0446	$154.04	$154.05	$154.00
Purchase #2	$243.56	11.344%	$271.1894	$271.19	$271.20	$271.20
Purchase #3	$231.84	8.206%	$250.8648	$250.86	$250.85	$250.90
Purchase #4	$123.92	4.330%	$129.2857	$129.29	$129.30	$129.30
Purchase #5	$228.89	10.844%	$253.7108	$253.71	$253.70	$253.70
Purchase #6	$31.73	13.658%	$36.0637	$36.06	$36.05	$36.10
Purchase #7	$80.96	11.712%	$90.442	$90.44	$90.45	$90.40
7 purchase totals =	$1,089.79		$1,185.6010	$1,185.59	$1,185.60	$1,185.60