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	$67.44	6.151%	$71.5882	$71.59	$71.60	$71.60
Purchase #2	$105.51	5.678%	$111.5009	$111.50	$111.50	$111.50
Purchase #3	$175.83	6.237%	$186.7965	$186.80	$186.80	$186.80
Purchase #4	$244.56	9.823%	$268.5831	$268.58	$268.60	$268.60
Purchase #5	$219.75	10.126%	$242.0019	$242.00	$242.00	$242.00
Purchase #6	$50.84	5.296%	$53.5325	$53.53	$53.55	$53.50
Purchase #7	$153.77	11.206%	$171.0015	$171.00	$171.00	$171.00
7 purchase totals =	$1,017.70		$1,105.0046	$1,105.00	$1,105.05	$1,105.00