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	$210.30	4.275%	$219.2903	$219.29	$219.30	$219.30
Purchase #2	$149.36	6.858%	$159.6031	$159.60	$159.60	$159.60
Purchase #3	$174.28	9.831%	$191.4135	$191.41	$191.40	$191.40
Purchase #4	$28.44	12.566%	$32.0138	$32.01	$32.00	$32.00
Purchase #5	$23.50	3.632%	$24.3535	$24.35	$24.35	$24.40
Purchase #6	$191.54	12.410%	$215.3101	$215.31	$215.30	$215.30
Purchase #7	$188.51	6.313%	$200.4106	$200.41	$200.40	$200.40
7 purchase totals =	$965.93		$1,042.3949	$1,042.38	$1,042.35	$1,042.40