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	$188.76	13.300%	$213.8651	$213.87	$213.85	$213.90
Purchase #2	$146.93	11.627%	$164.0136	$164.01	$164.00	$164.00
Purchase #3	$139.79	7.626%	$150.4504	$150.45	$150.45	$150.50
Purchase #4	$233.68	6.372%	$248.5701	$248.57	$248.55	$248.60
Purchase #5	$107.41	13.521%	$121.9329	$121.93	$121.95	$121.90
Purchase #6	$168.54	12.514%	$189.6311	$189.63	$189.65	$189.60
Purchase #7	$65.61	3.443%	$67.869	$67.87	$67.85	$67.90
7 purchase totals =	$1,050.72		$1,156.3322	$1,156.33	$1,156.30	$1,156.40