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	$89.40	10.439%	$98.7325	$98.73	$98.75	$98.70
Purchase #2	$200.53	11.403%	$223.3964	$223.40	$223.40	$223.40
Purchase #3	$40.32	11.780%	$45.0697	$45.07	$45.05	$45.10
Purchase #4	$41.71	12.256%	$46.822	$46.82	$46.80	$46.80
Purchase #5	$97.33	10.383%	$107.4358	$107.44	$107.45	$107.40
Purchase #6	$204.48	8.293%	$221.4375	$221.44	$221.45	$221.40
Purchase #7	$234.64	6.817%	$250.6354	$250.64	$250.65	$250.60
7 purchase totals =	$908.41		$993.5293	$993.54	$993.55	$993.40