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	$186.57	6.567%	$198.8221	$198.82	$198.80	$198.80
Purchase #2	$232.84	10.765%	$257.9052	$257.91	$257.90	$257.90
Purchase #3	$30.71	3.144%	$31.6755	$31.68	$31.70	$31.70
Purchase #4	$168.82	10.119%	$185.9029	$185.90	$185.90	$185.90
Purchase #5	$56.43	5.198%	$59.3632	$59.36	$59.35	$59.40
Purchase #6	$46.91	12.313%	$52.686	$52.69	$52.70	$52.70
Purchase #7	$225.33	11.131%	$250.4115	$250.41	$250.40	$250.40
7 purchase totals =	$947.61		$1,036.7664	$1,036.77	$1,036.75	$1,036.80