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	$59.44	9.840%	$65.2889	$65.29	$65.30	$65.30
Purchase #2	$73.61	9.681%	$80.7362	$80.74	$80.75	$80.70
Purchase #3	$67.73	7.268%	$72.6526	$72.65	$72.65	$72.70
Purchase #4	$147.28	4.165%	$153.4142	$153.41	$153.40	$153.40
Purchase #5	$54.41	13.708%	$61.8685	$61.87	$61.85	$61.90
Purchase #6	$138.91	10.580%	$153.6067	$153.61	$153.60	$153.60
Purchase #7	$156.88	11.484%	$174.8961	$174.90	$174.90	$174.90
7 purchase totals =	$698.26		$762.4632	$762.47	$762.45	$762.50