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	$48.35	4.712%	$50.6283	$50.63	$50.65	$50.60
Purchase #2	$112.63	3.349%	$116.402	$116.40	$116.40	$116.40
Purchase #3	$172.73	6.529%	$184.0075	$184.01	$184.00	$184.00
Purchase #4	$173.77	3.527%	$179.8989	$179.90	$179.90	$179.90
Purchase #5	$182.68	7.322%	$196.0558	$196.06	$196.05	$196.10
Purchase #6	$153.51	11.597%	$171.3126	$171.31	$171.30	$171.30
Purchase #7	$157.44	9.186%	$171.9024	$171.90	$171.90	$171.90
7 purchase totals =	$1,001.11		$1,070.2075	$1,070.21	$1,070.20	$1,070.20