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	$155.77	8.366%	$168.8017	$168.80	$168.80	$168.80
Purchase #2	$39.78	3.219%	$41.0605	$41.06	$41.05	$41.10
Purchase #3	$32.74	13.356%	$37.1128	$37.11	$37.10	$37.10
Purchase #4	$92.37	8.124%	$99.8741	$99.87	$99.85	$99.90
Purchase #5	$233.54	13.568%	$265.2267	$265.23	$265.25	$265.20
Purchase #6	$37.89	12.707%	$42.7047	$42.70	$42.70	$42.70
Purchase #7	$107.95	5.201%	$113.5645	$113.56	$113.55	$113.60
7 purchase totals =	$700.04		$768.3450	$768.33	$768.30	$768.40