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	$34.49	7.336%	$37.0202	$37.02	$37.00	$37.00
Purchase #2	$81.75	9.608%	$89.6045	$89.60	$89.60	$89.60
Purchase #3	$81.93	11.787%	$91.5871	$91.59	$91.60	$91.60
Purchase #4	$247.91	11.189%	$275.6486	$275.65	$275.65	$275.60
Purchase #5	$191.53	4.442%	$200.0378	$200.04	$200.05	$200.00
Purchase #6	$67.47	9.827%	$74.1003	$74.10	$74.10	$74.10
Purchase #7	$174.61	6.239%	$185.5039	$185.50	$185.50	$185.50
7 purchase totals =	$879.69		$953.5024	$953.50	$953.50	$953.40