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	$206.77	8.567%	$224.484	$224.48	$224.50	$224.50
Purchase #2	$195.33	6.385%	$207.8018	$207.80	$207.80	$207.80
Purchase #3	$74.82	11.560%	$83.4692	$83.47	$83.45	$83.50
Purchase #4	$87.29	10.503%	$96.4581	$96.46	$96.45	$96.50
Purchase #5	$82.96	6.721%	$88.5357	$88.54	$88.55	$88.50
Purchase #6	$159.32	5.688%	$168.3821	$168.38	$168.40	$168.40
Purchase #7	$125.90	6.497%	$134.0797	$134.08	$134.10	$134.10
7 purchase totals =	$932.39		$1,003.2106	$1,003.21	$1,003.25	$1,003.30