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	$154.86	13.411%	$175.6283	$175.63	$175.65	$175.60
Purchase #2	$211.82	5.177%	$222.7859	$222.79	$222.80	$222.80
Purchase #3	$20.88	11.295%	$23.2384	$23.24	$23.25	$23.20
Purchase #4	$37.36	13.387%	$42.3614	$42.36	$42.35	$42.40
Purchase #5	$248.81	4.399%	$259.7552	$259.76	$259.75	$259.80
Purchase #6	$206.65	9.177%	$225.6143	$225.61	$225.60	$225.60
Purchase #7	$84.72	5.302%	$89.2119	$89.21	$89.20	$89.20
7 purchase totals =	$965.10		$1,038.5954	$1,038.60	$1,038.60	$1,038.60