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	$131.88	13.498%	$149.6812	$149.68	$149.70	$149.70
Purchase #2	$20.81	4.845%	$21.8182	$21.82	$21.80	$21.80
Purchase #3	$140.34	3.489%	$145.2365	$145.24	$145.25	$145.20
Purchase #4	$27.88	12.777%	$31.4422	$31.44	$31.45	$31.40
Purchase #5	$173.96	12.764%	$196.1643	$196.16	$196.15	$196.20
Purchase #6	$6.53	7.711%	$7.0335	$7.03	$7.05	$7.00
Purchase #7	$240.45	5.799%	$254.3937	$254.39	$254.40	$254.40
7 purchase totals =	$741.85		$805.7696	$805.76	$805.80	$805.70