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	$60.90	5.771%	$64.4145	$64.41	$64.40	$64.40
Purchase #2	$180.74	8.371%	$195.8697	$195.87	$195.85	$195.90
Purchase #3	$118.94	7.451%	$127.8022	$127.80	$127.80	$127.80
Purchase #4	$145.88	10.277%	$160.8721	$160.87	$160.85	$160.90
Purchase #5	$60.46	11.783%	$67.584	$67.58	$67.60	$67.60
Purchase #6	$42.85	10.844%	$47.4967	$47.50	$47.50	$47.50
Purchase #7	$97.88	11.645%	$109.2781	$109.28	$109.30	$109.30
7 purchase totals =	$707.65		$773.3173	$773.31	$773.30	$773.40