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	$59.61	8.857%	$64.8897	$64.89	$64.90	$64.90
Purchase #2	$83.56	10.150%	$92.0413	$92.04	$92.05	$92.00
Purchase #3	$176.92	6.698%	$188.7701	$188.77	$188.75	$188.80
Purchase #4	$89.88	7.678%	$96.781	$96.78	$96.80	$96.80
Purchase #5	$194.59	10.810%	$215.6252	$215.63	$215.65	$215.60
Purchase #6	$90.34	8.449%	$97.9728	$97.97	$97.95	$98.00
Purchase #7	$185.90	3.718%	$192.8118	$192.81	$192.80	$192.80
7 purchase totals =	$880.80		$948.8919	$948.89	$948.90	$948.90