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	$200.61	13.457%	$227.6061	$227.61	$227.60	$227.60
Purchase #2	$23.27	5.655%	$24.5859	$24.59	$24.60	$24.60
Purchase #3	$82.65	8.539%	$89.7075	$89.71	$89.70	$89.70
Purchase #4	$176.91	13.140%	$200.156	$200.16	$200.15	$200.20
Purchase #5	$82.28	3.516%	$85.173	$85.17	$85.15	$85.20
Purchase #6	$77.59	7.713%	$83.5745	$83.57	$83.55	$83.60
Purchase #7	$189.62	12.682%	$213.6676	$213.67	$213.65	$213.70
7 purchase totals =	$832.93		$924.4706	$924.48	$924.40	$924.60