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	$43.59	4.729%	$45.6514	$45.65	$45.65	$45.70
Purchase #2	$180.88	13.415%	$205.1451	$205.15	$205.15	$205.10
Purchase #3	$186.30	5.623%	$196.7756	$196.78	$196.80	$196.80
Purchase #4	$37.84	12.466%	$42.5571	$42.56	$42.55	$42.60
Purchase #5	$15.64	8.123%	$16.9104	$16.91	$16.90	$16.90
Purchase #6	$30.34	12.435%	$34.1128	$34.11	$34.10	$34.10
Purchase #7	$167.64	12.398%	$188.424	$188.42	$188.40	$188.40
7 purchase totals =	$662.23		$729.5764	$729.58	$729.55	$729.60