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	$79.37	5.346%	$83.6131	$83.61	$83.60	$83.60
Purchase #2	$176.53	11.433%	$196.7127	$196.71	$196.70	$196.70
Purchase #3	$194.38	3.464%	$201.1133	$201.11	$201.10	$201.10
Purchase #4	$98.63	3.785%	$102.3631	$102.36	$102.35	$102.40
Purchase #5	$69.56	3.293%	$71.8506	$71.85	$71.85	$71.90
Purchase #6	$130.76	5.710%	$138.2264	$138.23	$138.25	$138.20
Purchase #7	$94.39	10.807%	$104.5907	$104.59	$104.60	$104.60
7 purchase totals =	$843.62		$898.4699	$898.46	$898.45	$898.50