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	$232.26	12.550%	$261.4086	$261.41	$261.40	$261.40
Purchase #2	$45.28	6.754%	$48.3382	$48.34	$48.35	$48.30
Purchase #3	$220.31	6.128%	$233.8106	$233.81	$233.80	$233.80
Purchase #4	$80.93	11.874%	$90.5396	$90.54	$90.55	$90.50
Purchase #5	$140.26	6.602%	$149.52	$149.52	$149.50	$149.50
Purchase #6	$114.59	12.581%	$129.0066	$129.01	$129.00	$129.00
Purchase #7	$209.46	13.685%	$238.1246	$238.12	$238.10	$238.10
7 purchase totals =	$1,043.09		$1,150.7482	$1,150.75	$1,150.70	$1,150.60