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	$109.55	4.759%	$114.7635	$114.76	$114.75	$114.80
Purchase #2	$135.65	5.424%	$143.0077	$143.01	$143.00	$143.00
Purchase #3	$53.89	7.197%	$57.7685	$57.77	$57.75	$57.80
Purchase #4	$71.45	11.859%	$79.9233	$79.92	$79.90	$79.90
Purchase #5	$80.37	6.717%	$85.7685	$85.77	$85.75	$85.80
Purchase #6	$35.83	12.594%	$40.3424	$40.34	$40.35	$40.30
Purchase #7	$223.31	9.691%	$244.951	$244.95	$244.95	$245.00
7 purchase totals =	$710.05		$766.5249	$766.52	$766.45	$766.60