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	$98.88	12.116%	$110.8603	$110.86	$110.85	$110.90
Purchase #2	$181.76	8.259%	$196.7716	$196.77	$196.75	$196.80
Purchase #3	$178.88	11.720%	$199.8447	$199.84	$199.85	$199.80
Purchase #4	$96.42	5.141%	$101.377	$101.38	$101.40	$101.40
Purchase #5	$78.72	6.842%	$84.106	$84.11	$84.10	$84.10
Purchase #6	$80.27	12.644%	$90.4193	$90.42	$90.40	$90.40
Purchase #7	$57.84	6.681%	$61.7043	$61.70	$61.70	$61.70
7 purchase totals =	$772.77		$845.0832	$845.08	$845.05	$845.10