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	$79.64	7.430%	$85.5573	$85.56	$85.55	$85.60
Purchase #2	$10.39	11.183%	$11.5519	$11.55	$11.55	$11.60
Purchase #3	$109.60	12.604%	$123.414	$123.41	$123.40	$123.40
Purchase #4	$229.72	3.550%	$237.8751	$237.88	$237.90	$237.90
Purchase #5	$42.54	8.620%	$46.2069	$46.21	$46.20	$46.20
Purchase #6	$48.35	13.156%	$54.7109	$54.71	$54.70	$54.70
Purchase #7	$109.71	5.573%	$115.8241	$115.82	$115.80	$115.80
7 purchase totals =	$629.95		$675.1402	$675.14	$675.10	$675.20