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	$168.55	10.787%	$186.7315	$186.73	$186.75	$186.70
Purchase #2	$40.85	7.243%	$43.8088	$43.81	$43.80	$43.80
Purchase #3	$149.72	10.524%	$165.4765	$165.48	$165.50	$165.50
Purchase #4	$185.52	9.665%	$203.4505	$203.45	$203.45	$203.50
Purchase #5	$109.56	9.485%	$119.9518	$119.95	$119.95	$120.00
Purchase #6	$45.27	5.844%	$47.9156	$47.92	$47.90	$47.90
Purchase #7	$108.33	9.779%	$118.9236	$118.92	$118.90	$118.90
7 purchase totals =	$807.80		$886.2583	$886.26	$886.25	$886.30