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	$175.32	5.399%	$184.7855	$184.79	$184.80	$184.80
Purchase #2	$41.62	3.167%	$42.9381	$42.94	$42.95	$42.90
Purchase #3	$83.49	6.372%	$88.81	$88.81	$88.80	$88.80
Purchase #4	$237.37	12.860%	$267.8958	$267.90	$267.90	$267.90
Purchase #5	$231.72	12.154%	$259.8832	$259.88	$259.90	$259.90
Purchase #6	$33.44	13.157%	$37.8397	$37.84	$37.85	$37.80
Purchase #7	$168.42	8.102%	$182.0654	$182.07	$182.05	$182.10
7 purchase totals =	$971.38		$1,064.2177	$1,064.23	$1,064.25	$1,064.20