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	$181.49	8.168%	$196.3141	$196.31	$196.30	$196.30
Purchase #2	$171.35	8.347%	$185.6526	$185.65	$185.65	$185.70
Purchase #3	$30.46	9.760%	$33.4329	$33.43	$33.45	$33.40
Purchase #4	$71.91	4.150%	$74.8943	$74.89	$74.90	$74.90
Purchase #5	$11.97	6.436%	$12.7404	$12.74	$12.75	$12.70
Purchase #6	$115.85	6.196%	$123.0281	$123.03	$123.05	$123.00
Purchase #7	$159.73	5.599%	$168.6733	$168.67	$168.65	$168.70
7 purchase totals =	$742.76		$794.7357	$794.72	$794.75	$794.70