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	$42.69	8.265%	$46.2183	$46.22	$46.20	$46.20
Purchase #2	$240.57	3.606%	$249.245	$249.25	$249.25	$249.20
Purchase #3	$23.62	3.371%	$24.4162	$24.42	$24.40	$24.40
Purchase #4	$211.54	13.765%	$240.6585	$240.66	$240.65	$240.70
Purchase #5	$244.39	9.608%	$267.871	$267.87	$267.85	$267.90
Purchase #6	$112.84	13.784%	$128.3939	$128.39	$128.40	$128.40
Purchase #7	$89.75	10.822%	$99.4627	$99.46	$99.45	$99.50
7 purchase totals =	$965.40		$1,056.2656	$1,056.27	$1,056.20	$1,056.30