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	$119.44	9.739%	$131.0723	$131.07	$131.05	$131.10
Purchase #2	$65.86	13.179%	$74.5397	$74.54	$74.55	$74.50
Purchase #3	$228.28	9.138%	$249.1402	$249.14	$249.15	$249.10
Purchase #4	$49.77	5.607%	$52.5606	$52.56	$52.55	$52.60
Purchase #5	$12.27	4.645%	$12.8399	$12.84	$12.85	$12.80
Purchase #6	$147.66	11.425%	$164.5302	$164.53	$164.55	$164.50
Purchase #7	$155.41	4.632%	$162.6086	$162.61	$162.60	$162.60
7 purchase totals =	$778.69		$847.2915	$847.29	$847.30	$847.20