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	$150.96	9.444%	$165.2167	$165.22	$165.20	$165.20
Purchase #2	$160.33	4.447%	$167.4599	$167.46	$167.45	$167.50
Purchase #3	$147.98	11.793%	$165.4313	$165.43	$165.45	$165.40
Purchase #4	$245.94	11.441%	$274.078	$274.08	$274.10	$274.10
Purchase #5	$87.63	5.356%	$92.3235	$92.32	$92.30	$92.30
Purchase #6	$184.92	3.365%	$191.1426	$191.14	$191.15	$191.10
Purchase #7	$53.28	11.452%	$59.3816	$59.38	$59.40	$59.40
7 purchase totals =	$1,031.04		$1,115.0336	$1,115.03	$1,115.05	$1,115.00