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	$66.39	5.763%	$70.2161	$70.22	$70.20	$70.20
Purchase #2	$126.95	11.223%	$141.1976	$141.20	$141.20	$141.20
Purchase #3	$51.97	5.136%	$54.6392	$54.64	$54.65	$54.60
Purchase #4	$78.77	4.442%	$82.269	$82.27	$82.25	$82.30
Purchase #5	$96.62	7.740%	$104.0984	$104.10	$104.10	$104.10
Purchase #6	$225.46	6.637%	$240.4238	$240.42	$240.40	$240.40
Purchase #7	$125.67	4.546%	$131.383	$131.38	$131.40	$131.40
7 purchase totals =	$771.83		$824.2271	$824.23	$824.20	$824.20