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	$186.70	3.870%	$193.9253	$193.93	$193.95	$193.90
Purchase #2	$169.82	6.793%	$181.3559	$181.36	$181.35	$181.40
Purchase #3	$100.77	10.371%	$111.2209	$111.22	$111.20	$111.20
Purchase #4	$21.35	5.402%	$22.5033	$22.50	$22.50	$22.50
Purchase #5	$63.78	7.235%	$68.3945	$68.39	$68.40	$68.40
Purchase #6	$125.33	13.548%	$142.3097	$142.31	$142.30	$142.30
Purchase #7	$35.82	11.275%	$39.8587	$39.86	$39.85	$39.90
7 purchase totals =	$703.57		$759.5683	$759.57	$759.55	$759.60