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	$189.77	9.679%	$208.1378	$208.14	$208.15	$208.10
Purchase #2	$98.69	5.216%	$103.8377	$103.84	$103.85	$103.80
Purchase #3	$202.72	10.158%	$223.3123	$223.31	$223.30	$223.30
Purchase #4	$200.25	13.751%	$227.7864	$227.79	$227.80	$227.80
Purchase #5	$121.55	3.860%	$126.2418	$126.24	$126.25	$126.20
Purchase #6	$249.94	6.181%	$265.3888	$265.39	$265.40	$265.40
Purchase #7	$69.41	13.286%	$78.6318	$78.63	$78.65	$78.60
7 purchase totals =	$1,132.33		$1,233.3366	$1,233.34	$1,233.40	$1,233.20