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	$98.75	7.801%	$106.4535	$106.45	$106.45	$106.50
Purchase #2	$146.36	9.542%	$160.3257	$160.33	$160.35	$160.30
Purchase #3	$103.97	5.271%	$109.4503	$109.45	$109.45	$109.50
Purchase #4	$151.31	13.873%	$172.3012	$172.30	$172.30	$172.30
Purchase #5	$32.33	5.619%	$34.1466	$34.15	$34.15	$34.10
Purchase #6	$142.96	5.754%	$151.1859	$151.19	$151.20	$151.20
Purchase #7	$176.63	8.481%	$191.61	$191.61	$191.60	$191.60
7 purchase totals =	$852.31		$925.4732	$925.48	$925.50	$925.50