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	$75.64	8.665%	$82.1942	$82.19	$82.20	$82.20
Purchase #2	$223.99	9.613%	$245.5222	$245.52	$245.50	$245.50
Purchase #3	$147.58	12.317%	$165.7574	$165.76	$165.75	$165.80
Purchase #4	$95.75	10.556%	$105.8574	$105.86	$105.85	$105.90
Purchase #5	$195.88	11.197%	$217.8127	$217.81	$217.80	$217.80
Purchase #6	$39.88	8.656%	$43.332	$43.33	$43.35	$43.30
Purchase #7	$221.25	9.791%	$242.9126	$242.91	$242.90	$242.90
7 purchase totals =	$999.97		$1,103.3885	$1,103.38	$1,103.35	$1,103.40