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	$33.44	13.820%	$38.0614	$38.06	$38.05	$38.10
Purchase #2	$85.48	12.810%	$96.43	$96.43	$96.45	$96.40
Purchase #3	$214.88	13.831%	$244.6001	$244.60	$244.60	$244.60
Purchase #4	$90.56	13.424%	$102.7168	$102.72	$102.70	$102.70
Purchase #5	$109.47	13.826%	$124.6053	$124.61	$124.60	$124.60
Purchase #6	$167.43	7.318%	$179.6825	$179.68	$179.70	$179.70
Purchase #7	$44.91	4.206%	$46.7989	$46.80	$46.80	$46.80
7 purchase totals =	$746.17		$832.8950	$832.90	$832.90	$832.90