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	$219.91	13.461%	$249.5121	$249.51	$249.50	$249.50
Purchase #2	$75.65	13.222%	$85.6524	$85.65	$85.65	$85.70
Purchase #3	$70.52	9.469%	$77.1975	$77.20	$77.20	$77.20
Purchase #4	$216.38	10.595%	$239.3055	$239.31	$239.30	$239.30
Purchase #5	$70.62	10.621%	$78.1206	$78.12	$78.10	$78.10
Purchase #6	$178.46	3.748%	$185.1487	$185.15	$185.15	$185.10
Purchase #7	$191.48	12.554%	$215.5184	$215.52	$215.50	$215.50
7 purchase totals =	$1,023.02		$1,130.4552	$1,130.46	$1,130.40	$1,130.40