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	$22.55	3.300%	$23.2942	$23.29	$23.30	$23.30
Purchase #2	$27.54	13.871%	$31.3601	$31.36	$31.35	$31.40
Purchase #3	$85.53	4.688%	$89.5396	$89.54	$89.55	$89.50
Purchase #4	$90.91	7.850%	$98.0464	$98.05	$98.05	$98.00
Purchase #5	$237.99	5.388%	$250.8129	$250.81	$250.80	$250.80
Purchase #6	$223.38	3.407%	$230.9906	$230.99	$231.00	$231.00
Purchase #7	$58.56	6.607%	$62.4291	$62.43	$62.45	$62.40
7 purchase totals =	$746.46		$786.4729	$786.47	$786.50	$786.40