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	$97.73	11.496%	$108.965	$108.97	$108.95	$109.00
Purchase #2	$243.85	12.294%	$273.8289	$273.83	$273.85	$273.80
Purchase #3	$73.52	10.284%	$81.0808	$81.08	$81.10	$81.10
Purchase #4	$33.34	12.589%	$37.5372	$37.54	$37.55	$37.50
Purchase #5	$234.77	9.415%	$256.8736	$256.87	$256.85	$256.90
Purchase #6	$71.90	13.310%	$81.4699	$81.47	$81.45	$81.50
Purchase #7	$200.79	13.813%	$228.5251	$228.53	$228.55	$228.50
7 purchase totals =	$955.90		$1,068.2805	$1,068.29	$1,068.30	$1,068.30