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	$49.57	3.471%	$51.2906	$51.29	$51.30	$51.30
Purchase #2	$130.51	10.580%	$144.318	$144.32	$144.30	$144.30
Purchase #3	$48.46	13.535%	$55.0191	$55.02	$55.00	$55.00
Purchase #4	$130.40	13.235%	$147.6584	$147.66	$147.65	$147.70
Purchase #5	$182.36	13.390%	$206.778	$206.78	$206.80	$206.80
Purchase #6	$244.35	12.652%	$275.2652	$275.27	$275.25	$275.30
Purchase #7	$237.72	10.450%	$262.5617	$262.56	$262.55	$262.60
7 purchase totals =	$1,023.37		$1,142.8910	$1,142.90	$1,142.85	$1,143.00