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	$198.29	13.483%	$225.0254	$225.03	$225.05	$225.00
Purchase #2	$62.46	5.480%	$65.8828	$65.88	$65.90	$65.90
Purchase #3	$200.81	10.709%	$222.3147	$222.31	$222.30	$222.30
Purchase #4	$157.61	7.505%	$169.4386	$169.44	$169.45	$169.40
Purchase #5	$23.87	12.431%	$26.8373	$26.84	$26.85	$26.80
Purchase #6	$213.96	4.129%	$222.7944	$222.79	$222.80	$222.80
Purchase #7	$150.88	7.619%	$162.3755	$162.38	$162.40	$162.40
7 purchase totals =	$1,007.88		$1,094.6687	$1,094.67	$1,094.75	$1,094.60