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	$176.27	5.197%	$185.4308	$185.43	$185.45	$185.40
Purchase #2	$96.95	9.227%	$105.8956	$105.90	$105.90	$105.90
Purchase #3	$40.62	12.277%	$45.6069	$45.61	$45.60	$45.60
Purchase #4	$28.83	9.606%	$31.5994	$31.60	$31.60	$31.60
Purchase #5	$244.38	11.578%	$272.6743	$272.67	$272.65	$272.70
Purchase #6	$112.76	13.838%	$128.3637	$128.36	$128.35	$128.40
Purchase #7	$162.49	10.198%	$179.0607	$179.06	$179.05	$179.10
7 purchase totals =	$862.30		$948.6314	$948.63	$948.60	$948.70