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	$31.25	12.487%	$35.1522	$35.15	$35.15	$35.20
Purchase #2	$188.71	13.792%	$214.7369	$214.74	$214.75	$214.70
Purchase #3	$128.63	13.600%	$146.1237	$146.12	$146.10	$146.10
Purchase #4	$177.79	4.334%	$185.4954	$185.50	$185.50	$185.50
Purchase #5	$64.84	11.829%	$72.5099	$72.51	$72.50	$72.50
Purchase #6	$171.42	9.705%	$188.0563	$188.06	$188.05	$188.10
Purchase #7	$148.72	13.374%	$168.6098	$168.61	$168.60	$168.60
7 purchase totals =	$911.36		$1,010.6842	$1,010.69	$1,010.65	$1,010.70