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	$69.94	3.385%	$72.3075	$72.31	$72.30	$72.30
Purchase #2	$73.40	11.394%	$81.7632	$81.76	$81.75	$81.80
Purchase #3	$243.54	6.666%	$259.7744	$259.77	$259.75	$259.80
Purchase #4	$95.71	12.224%	$107.4096	$107.41	$107.40	$107.40
Purchase #5	$211.47	6.342%	$224.8814	$224.88	$224.90	$224.90
Purchase #6	$64.26	12.315%	$72.1736	$72.17	$72.15	$72.20
Purchase #7	$144.60	4.410%	$150.9769	$150.98	$151.00	$151.00
7 purchase totals =	$902.92		$969.2866	$969.28	$969.25	$969.40