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	$207.85	3.241%	$214.5864	$214.59	$214.60	$214.60
Purchase #2	$67.31	7.169%	$72.1355	$72.14	$72.15	$72.10
Purchase #3	$96.56	6.201%	$102.5477	$102.55	$102.55	$102.50
Purchase #4	$225.48	11.706%	$251.8747	$251.87	$251.85	$251.90
Purchase #5	$162.61	13.298%	$184.2339	$184.23	$184.25	$184.20
Purchase #6	$229.91	4.489%	$240.2307	$240.23	$240.25	$240.20
Purchase #7	$26.32	9.451%	$28.8075	$28.81	$28.80	$28.80
7 purchase totals =	$1,016.04		$1,094.4164	$1,094.42	$1,094.45	$1,094.30