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	$65.47	4.500%	$68.4162	$68.42	$68.40	$68.40
Purchase #2	$215.69	8.330%	$233.657	$233.66	$233.65	$233.70
Purchase #3	$157.86	7.748%	$170.091	$170.09	$170.10	$170.10
Purchase #4	$186.45	5.517%	$196.7364	$196.74	$196.75	$196.70
Purchase #5	$189.73	5.857%	$200.8425	$200.84	$200.85	$200.80
Purchase #6	$57.53	12.333%	$64.6252	$64.63	$64.65	$64.60
Purchase #7	$79.89	11.690%	$89.2291	$89.23	$89.25	$89.20
7 purchase totals =	$952.62		$1,023.5974	$1,023.61	$1,023.65	$1,023.50