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	$162.70	4.381%	$169.8279	$169.83	$169.85	$169.80
Purchase #2	$42.34	4.169%	$44.1052	$44.11	$44.10	$44.10
Purchase #3	$28.73	13.550%	$32.6229	$32.62	$32.60	$32.60
Purchase #4	$193.42	3.799%	$200.768	$200.77	$200.75	$200.80
Purchase #5	$242.87	8.693%	$263.9827	$263.98	$264.00	$264.00
Purchase #6	$66.81	9.850%	$73.3908	$73.39	$73.40	$73.40
Purchase #7	$45.38	13.642%	$51.5707	$51.57	$51.55	$51.60
7 purchase totals =	$782.25		$836.2682	$836.27	$836.25	$836.30