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	$243.34	5.309%	$256.2589	$256.26	$256.25	$256.30
Purchase #2	$97.82	6.270%	$103.9533	$103.95	$103.95	$104.00
Purchase #3	$35.36	6.497%	$37.6573	$37.66	$37.65	$37.70
Purchase #4	$62.56	7.594%	$67.3108	$67.31	$67.30	$67.30
Purchase #5	$245.73	6.850%	$262.5625	$262.56	$262.55	$262.60
Purchase #6	$18.56	12.530%	$20.8856	$20.89	$20.90	$20.90
Purchase #7	$139.97	11.749%	$156.4151	$156.42	$156.40	$156.40
7 purchase totals =	$843.34		$905.0435	$905.05	$905.00	$905.20