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	$203.31	4.640%	$212.7436	$212.74	$212.75	$212.70
Purchase #2	$51.45	6.410%	$54.7479	$54.75	$54.75	$54.70
Purchase #3	$13.56	4.429%	$14.1606	$14.16	$14.15	$14.20
Purchase #4	$170.97	10.850%	$189.5202	$189.52	$189.50	$189.50
Purchase #5	$43.94	11.116%	$48.8244	$48.82	$48.80	$48.80
Purchase #6	$117.30	8.369%	$127.1168	$127.12	$127.10	$127.10
Purchase #7	$180.84	8.734%	$196.6346	$196.63	$196.65	$196.60
7 purchase totals =	$781.37		$843.7481	$843.74	$843.70	$843.60