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	$115.43	11.828%	$129.0831	$129.08	$129.10	$129.10
Purchase #2	$229.81	5.807%	$243.1551	$243.16	$243.15	$243.20
Purchase #3	$108.89	8.747%	$118.4146	$118.41	$118.40	$118.40
Purchase #4	$89.39	11.728%	$99.8737	$99.87	$99.85	$99.90
Purchase #5	$172.55	4.484%	$180.2871	$180.29	$180.30	$180.30
Purchase #6	$165.54	10.774%	$183.3753	$183.38	$183.40	$183.40
Purchase #7	$95.83	9.783%	$105.205	$105.21	$105.20	$105.20
7 purchase totals =	$977.44		$1,059.3939	$1,059.40	$1,059.40	$1,059.50