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	$240.44	3.406%	$248.6294	$248.63	$248.65	$248.60
Purchase #2	$101.99	5.681%	$107.7841	$107.78	$107.80	$107.80
Purchase #3	$176.45	11.588%	$196.897	$196.90	$196.90	$196.90
Purchase #4	$222.33	3.395%	$229.8781	$229.88	$229.90	$229.90
Purchase #5	$99.35	4.121%	$103.4442	$103.44	$103.45	$103.40
Purchase #6	$25.69	5.503%	$27.1037	$27.10	$27.10	$27.10
Purchase #7	$244.31	13.294%	$276.7886	$276.79	$276.80	$276.80
7 purchase totals =	$1,110.56		$1,190.5251	$1,190.52	$1,190.60	$1,190.50