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	$211.39	10.829%	$234.2814	$234.28	$234.30	$234.30
Purchase #2	$164.89	4.334%	$172.0363	$172.04	$172.05	$172.00
Purchase #3	$188.94	6.148%	$200.556	$200.56	$200.55	$200.60
Purchase #4	$105.62	10.710%	$116.9319	$116.93	$116.95	$116.90
Purchase #5	$30.36	7.409%	$32.6094	$32.61	$32.60	$32.60
Purchase #6	$69.47	6.579%	$74.0404	$74.04	$74.05	$74.00
Purchase #7	$225.52	9.710%	$247.418	$247.42	$247.40	$247.40
7 purchase totals =	$996.19		$1,077.8734	$1,077.88	$1,077.90	$1,077.80