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	$210.74	5.530%	$222.3939	$222.39	$222.40	$222.40
Purchase #2	$150.47	9.256%	$164.3975	$164.40	$164.40	$164.40
Purchase #3	$180.83	5.419%	$190.6292	$190.63	$190.65	$190.60
Purchase #4	$204.43	9.850%	$224.5664	$224.57	$224.55	$224.60
Purchase #5	$96.42	5.865%	$102.075	$102.08	$102.10	$102.10
Purchase #6	$77.84	13.385%	$88.2589	$88.26	$88.25	$88.30
Purchase #7	$61.98	13.553%	$70.3801	$70.38	$70.40	$70.40
7 purchase totals =	$982.71		$1,062.7010	$1,062.71	$1,062.75	$1,062.80