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	$98.55	11.582%	$109.9641	$109.96	$109.95	$110.00
Purchase #2	$233.77	5.613%	$246.8915	$246.89	$246.90	$246.90
Purchase #3	$52.25	4.585%	$54.6457	$54.65	$54.65	$54.60
Purchase #4	$75.32	11.363%	$83.8786	$83.88	$83.90	$83.90
Purchase #5	$221.98	10.756%	$245.8562	$245.86	$245.85	$245.90
Purchase #6	$120.31	11.764%	$134.4633	$134.46	$134.45	$134.50
Purchase #7	$31.32	13.474%	$35.5401	$35.54	$35.55	$35.50
7 purchase totals =	$833.50		$911.2395	$911.24	$911.25	$911.30