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	$115.91	10.282%	$127.8279	$127.83	$127.85	$127.80
Purchase #2	$35.31	6.455%	$37.5893	$37.59	$37.60	$37.60
Purchase #3	$47.42	12.329%	$53.2664	$53.27	$53.25	$53.30
Purchase #4	$54.35	11.287%	$60.4845	$60.48	$60.50	$60.50
Purchase #5	$138.36	7.681%	$148.9874	$148.99	$149.00	$149.00
Purchase #6	$143.51	3.482%	$148.507	$148.51	$148.50	$148.50
Purchase #7	$165.59	3.502%	$171.389	$171.39	$171.40	$171.40
7 purchase totals =	$700.45		$748.0515	$748.06	$748.10	$748.10