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	$224.44	7.719%	$241.7645	$241.76	$241.75	$241.80
Purchase #2	$215.56	11.772%	$240.9357	$240.94	$240.95	$240.90
Purchase #3	$79.32	13.133%	$89.7371	$89.74	$89.75	$89.70
Purchase #4	$64.72	10.595%	$71.5771	$71.58	$71.60	$71.60
Purchase #5	$45.65	7.562%	$49.1021	$49.10	$49.10	$49.10
Purchase #6	$150.85	7.578%	$162.2814	$162.28	$162.30	$162.30
Purchase #7	$209.54	8.760%	$227.8957	$227.90	$227.90	$227.90
7 purchase totals =	$990.08		$1,083.2936	$1,083.30	$1,083.35	$1,083.30