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	$100.46	5.252%	$105.7362	$105.74	$105.75	$105.70
Purchase #2	$150.45	6.715%	$160.5527	$160.55	$160.55	$160.60
Purchase #3	$121.79	4.609%	$127.4033	$127.40	$127.40	$127.40
Purchase #4	$224.73	12.773%	$253.4348	$253.43	$253.45	$253.40
Purchase #5	$12.52	8.410%	$13.5729	$13.57	$13.55	$13.60
Purchase #6	$58.41	9.648%	$64.0454	$64.05	$64.05	$64.00
Purchase #7	$140.51	6.773%	$150.0267	$150.03	$150.05	$150.00
7 purchase totals =	$808.87		$874.7720	$874.77	$874.80	$874.70