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	$125.63	6.220%	$133.4442	$133.44	$133.45	$133.40
Purchase #2	$31.97	4.238%	$33.3249	$33.32	$33.30	$33.30
Purchase #3	$108.41	13.635%	$123.1917	$123.19	$123.20	$123.20
Purchase #4	$183.63	7.190%	$196.833	$196.83	$196.85	$196.80
Purchase #5	$85.82	9.386%	$93.8751	$93.88	$93.90	$93.90
Purchase #6	$37.67	4.867%	$39.5034	$39.50	$39.50	$39.50
Purchase #7	$85.83	6.334%	$91.2665	$91.27	$91.25	$91.30
7 purchase totals =	$658.96		$711.4388	$711.43	$711.45	$711.40