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	$113.86	8.354%	$123.3719	$123.37	$123.35	$123.40
Purchase #2	$250.50	13.489%	$284.2899	$284.29	$284.30	$284.30
Purchase #3	$59.78	9.700%	$65.5787	$65.58	$65.60	$65.60
Purchase #4	$42.66	7.655%	$45.9256	$45.93	$45.95	$45.90
Purchase #5	$219.63	8.271%	$237.7956	$237.80	$237.80	$237.80
Purchase #6	$192.60	9.753%	$211.3843	$211.38	$211.40	$211.40
Purchase #7	$127.70	5.334%	$134.5115	$134.51	$134.50	$134.50
7 purchase totals =	$1,006.73		$1,102.8575	$1,102.86	$1,102.90	$1,102.90