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	$215.56	4.789%	$225.8832	$225.88	$225.90	$225.90
Purchase #2	$200.65	7.739%	$216.1783	$216.18	$216.20	$216.20
Purchase #3	$128.76	13.643%	$146.3267	$146.33	$146.35	$146.30
Purchase #4	$78.61	6.245%	$83.5192	$83.52	$83.50	$83.50
Purchase #5	$238.91	5.686%	$252.4944	$252.49	$252.50	$252.50
Purchase #6	$178.27	13.471%	$202.2848	$202.28	$202.30	$202.30
Purchase #7	$83.79	6.682%	$89.3888	$89.39	$89.40	$89.40
7 purchase totals =	$1,124.55		$1,216.0754	$1,216.07	$1,216.15	$1,216.10