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	$184.25	6.464%	$196.1599	$196.16	$196.15	$196.20
Purchase #2	$89.91	10.120%	$99.0089	$99.01	$99.00	$99.00
Purchase #3	$37.27	12.210%	$41.8207	$41.82	$41.80	$41.80
Purchase #4	$109.30	12.729%	$123.2128	$123.21	$123.20	$123.20
Purchase #5	$246.98	9.791%	$271.1618	$271.16	$271.15	$271.20
Purchase #6	$102.48	9.802%	$112.5251	$112.53	$112.55	$112.50
Purchase #7	$234.57	6.602%	$250.0563	$250.06	$250.05	$250.10
7 purchase totals =	$1,004.76		$1,093.9455	$1,093.95	$1,093.90	$1,094.00