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	$97.55	6.729%	$104.1141	$104.11	$104.10	$104.10
Purchase #2	$153.61	9.789%	$168.6469	$168.65	$168.65	$168.60
Purchase #3	$106.57	10.648%	$117.9176	$117.92	$117.90	$117.90
Purchase #4	$202.69	6.629%	$216.1263	$216.13	$216.15	$216.10
Purchase #5	$219.63	12.410%	$246.8861	$246.89	$246.90	$246.90
Purchase #6	$18.56	10.791%	$20.5628	$20.56	$20.55	$20.60
Purchase #7	$82.61	4.187%	$86.0689	$86.07	$86.05	$86.10
7 purchase totals =	$881.22		$960.3227	$960.33	$960.30	$960.30