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	$195.89	3.313%	$202.3798	$202.38	$202.40	$202.40
Purchase #2	$171.30	9.224%	$187.1007	$187.10	$187.10	$187.10
Purchase #3	$168.86	4.332%	$176.175	$176.18	$176.20	$176.20
Purchase #4	$100.79	10.156%	$111.0262	$111.03	$111.05	$111.00
Purchase #5	$172.58	10.541%	$190.7717	$190.77	$190.75	$190.80
Purchase #6	$99.55	6.425%	$105.9461	$105.95	$105.95	$105.90
Purchase #7	$110.56	6.534%	$117.784	$117.78	$117.80	$117.80
7 purchase totals =	$1,019.53		$1,091.1835	$1,091.19	$1,091.25	$1,091.20