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	$137.73	5.513%	$145.3231	$145.32	$145.30	$145.30
Purchase #2	$30.49	8.135%	$32.9704	$32.97	$32.95	$33.00
Purchase #3	$183.87	6.124%	$195.1302	$195.13	$195.15	$195.10
Purchase #4	$108.77	6.244%	$115.5616	$115.56	$115.55	$115.60
Purchase #5	$82.68	8.655%	$89.836	$89.84	$89.85	$89.80
Purchase #6	$218.30	4.725%	$228.6147	$228.61	$228.60	$228.60
Purchase #7	$75.98	3.436%	$78.5907	$78.59	$78.60	$78.60
7 purchase totals =	$837.82		$886.0267	$886.02	$886.00	$886.00