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	$43.41	9.568%	$47.5635	$47.56	$47.55	$47.60
Purchase #2	$173.33	11.790%	$193.7656	$193.77	$193.75	$193.80
Purchase #3	$78.34	10.455%	$86.5304	$86.53	$86.55	$86.50
Purchase #4	$185.54	3.788%	$192.5683	$192.57	$192.55	$192.60
Purchase #5	$115.63	6.824%	$123.5206	$123.52	$123.50	$123.50
Purchase #6	$21.70	13.107%	$24.5442	$24.54	$24.55	$24.50
Purchase #7	$73.89	11.628%	$82.4819	$82.48	$82.50	$82.50
7 purchase totals =	$691.84		$750.9745	$750.97	$750.95	$751.00