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	$187.49	9.544%	$205.384	$205.38	$205.40	$205.40
Purchase #2	$165.71	8.564%	$179.9014	$179.90	$179.90	$179.90
Purchase #3	$105.30	10.173%	$116.0122	$116.01	$116.00	$116.00
Purchase #4	$227.98	7.739%	$245.6234	$245.62	$245.60	$245.60
Purchase #5	$197.29	12.457%	$221.8664	$221.87	$221.85	$221.90
Purchase #6	$187.42	4.637%	$196.1107	$196.11	$196.10	$196.10
Purchase #7	$50.79	12.344%	$57.0595	$57.06	$57.05	$57.10
7 purchase totals =	$1,121.98		$1,221.9576	$1,221.95	$1,221.90	$1,222.00