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	$197.50	12.591%	$222.3672	$222.37	$222.35	$222.40
Purchase #2	$82.40	4.239%	$85.8929	$85.89	$85.90	$85.90
Purchase #3	$139.61	7.836%	$150.5498	$150.55	$150.55	$150.50
Purchase #4	$137.98	11.427%	$153.747	$153.75	$153.75	$153.70
Purchase #5	$221.41	6.609%	$236.043	$236.04	$236.05	$236.00
Purchase #6	$182.28	3.715%	$189.0517	$189.05	$189.05	$189.10
Purchase #7	$93.59	6.544%	$99.7145	$99.71	$99.70	$99.70
7 purchase totals =	$1,054.77		$1,137.3661	$1,137.36	$1,137.35	$1,137.30