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	$43.44	4.850%	$45.5468	$45.55	$45.55	$45.50
Purchase #2	$12.31	12.809%	$13.8868	$13.89	$13.90	$13.90
Purchase #3	$206.46	5.647%	$218.1188	$218.12	$218.10	$218.10
Purchase #4	$78.31	12.562%	$88.1473	$88.15	$88.15	$88.10
Purchase #5	$86.92	6.445%	$92.522	$92.52	$92.50	$92.50
Purchase #6	$85.81	7.551%	$92.2895	$92.29	$92.30	$92.30
Purchase #7	$51.46	5.782%	$54.4354	$54.44	$54.45	$54.40
7 purchase totals =	$564.71		$604.9466	$604.96	$604.95	$604.80