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	$219.36	11.571%	$244.7421	$244.74	$244.75	$244.70
Purchase #2	$85.64	7.147%	$91.7607	$91.76	$91.75	$91.80
Purchase #3	$46.67	6.292%	$49.6065	$49.61	$49.60	$49.60
Purchase #4	$78.95	13.112%	$89.3019	$89.30	$89.30	$89.30
Purchase #5	$175.62	13.246%	$198.8826	$198.88	$198.90	$198.90
Purchase #6	$57.94	11.699%	$64.7184	$64.72	$64.70	$64.70
Purchase #7	$131.61	4.469%	$137.4917	$137.49	$137.50	$137.50
7 purchase totals =	$795.79		$876.5039	$876.50	$876.50	$876.50