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	$153.26	10.228%	$168.9354	$168.94	$168.95	$168.90
Purchase #2	$98.44	4.673%	$103.0401	$103.04	$103.05	$103.00
Purchase #3	$231.80	3.587%	$240.1147	$240.11	$240.10	$240.10
Purchase #4	$11.28	7.571%	$12.134	$12.13	$12.15	$12.10
Purchase #5	$145.87	7.242%	$156.4339	$156.43	$156.45	$156.40
Purchase #6	$100.48	8.807%	$109.3293	$109.33	$109.35	$109.30
Purchase #7	$116.59	10.158%	$128.4332	$128.43	$128.45	$128.40
7 purchase totals =	$857.72		$918.4206	$918.41	$918.50	$918.20