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	$168.78	6.870%	$180.3752	$180.38	$180.40	$180.40
Purchase #2	$182.68	12.510%	$205.5333	$205.53	$205.55	$205.50
Purchase #3	$164.31	12.292%	$184.507	$184.51	$184.50	$184.50
Purchase #4	$180.30	8.340%	$195.337	$195.34	$195.35	$195.30
Purchase #5	$148.48	13.507%	$168.5352	$168.54	$168.55	$168.50
Purchase #6	$110.79	4.797%	$116.1046	$116.10	$116.10	$116.10
Purchase #7	$152.91	6.303%	$162.5479	$162.55	$162.55	$162.50
7 purchase totals =	$1,108.25		$1,212.9402	$1,212.95	$1,213.00	$1,212.80