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	$200.41	9.174%	$218.7956	$218.80	$218.80	$218.80
Purchase #2	$219.71	5.814%	$232.4839	$232.48	$232.50	$232.50
Purchase #3	$122.52	9.434%	$134.0785	$134.08	$134.10	$134.10
Purchase #4	$149.66	8.588%	$162.5128	$162.51	$162.50	$162.50
Purchase #5	$101.34	10.112%	$111.5875	$111.59	$111.60	$111.60
Purchase #6	$106.42	5.329%	$112.0911	$112.09	$112.10	$112.10
Purchase #7	$98.59	7.272%	$105.7595	$105.76	$105.75	$105.80
7 purchase totals =	$998.65		$1,077.3089	$1,077.31	$1,077.35	$1,077.40