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	$137.60	6.443%	$146.4656	$146.47	$146.45	$146.50
Purchase #2	$169.85	9.706%	$186.3356	$186.34	$186.35	$186.30
Purchase #3	$249.29	3.662%	$258.419	$258.42	$258.40	$258.40
Purchase #4	$152.83	13.276%	$173.1197	$173.12	$173.10	$173.10
Purchase #5	$106.44	4.563%	$111.2969	$111.30	$111.30	$111.30
Purchase #6	$89.32	11.558%	$99.6436	$99.64	$99.65	$99.60
Purchase #7	$115.56	3.532%	$119.6416	$119.64	$119.65	$119.60
7 purchase totals =	$1,020.89		$1,094.9220	$1,094.93	$1,094.90	$1,094.80