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	$153.42	4.663%	$160.574	$160.57	$160.55	$160.60
Purchase #2	$232.85	5.592%	$245.871	$245.87	$245.85	$245.90
Purchase #3	$151.81	9.170%	$165.731	$165.73	$165.75	$165.70
Purchase #4	$241.80	3.293%	$249.7625	$249.76	$249.75	$249.80
Purchase #5	$51.61	5.424%	$54.4093	$54.41	$54.40	$54.40
Purchase #6	$173.65	10.503%	$191.8885	$191.89	$191.90	$191.90
Purchase #7	$53.27	4.149%	$55.4802	$55.48	$55.50	$55.50
7 purchase totals =	$1,058.41		$1,123.7165	$1,123.71	$1,123.70	$1,123.80