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	$28.78	9.173%	$31.42	$31.42	$31.40	$31.40
Purchase #2	$103.74	9.217%	$113.3017	$113.30	$113.30	$113.30
Purchase #3	$104.96	6.245%	$111.5148	$111.51	$111.50	$111.50
Purchase #4	$91.97	3.181%	$94.8956	$94.90	$94.90	$94.90
Purchase #5	$249.63	10.152%	$274.9724	$274.97	$274.95	$275.00
Purchase #6	$241.60	5.428%	$254.714	$254.71	$254.70	$254.70
Purchase #7	$194.39	9.145%	$212.167	$212.17	$212.15	$212.20
7 purchase totals =	$1,015.07		$1,092.9855	$1,092.98	$1,092.90	$1,093.00