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	$173.76	6.767%	$185.5183	$185.52	$185.50	$185.50
Purchase #2	$39.32	8.451%	$42.6429	$42.64	$42.65	$42.60
Purchase #3	$37.38	6.328%	$39.7454	$39.75	$39.75	$39.70
Purchase #4	$123.70	4.196%	$128.8905	$128.89	$128.90	$128.90
Purchase #5	$134.43	9.659%	$147.4146	$147.41	$147.40	$147.40
Purchase #6	$209.82	12.158%	$235.3299	$235.33	$235.35	$235.30
Purchase #7	$231.50	6.228%	$245.9178	$245.92	$245.90	$245.90
7 purchase totals =	$949.91		$1,025.4594	$1,025.46	$1,025.45	$1,025.30