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	$73.53	6.755%	$78.497	$78.50	$78.50	$78.50
Purchase #2	$50.49	6.673%	$53.8592	$53.86	$53.85	$53.90
Purchase #3	$178.96	3.154%	$184.6044	$184.60	$184.60	$184.60
Purchase #4	$226.57	5.247%	$238.4581	$238.46	$238.45	$238.50
Purchase #5	$72.96	12.749%	$82.2617	$82.26	$82.25	$82.30
Purchase #6	$175.66	12.346%	$197.347	$197.35	$197.35	$197.30
Purchase #7	$146.69	12.743%	$165.3827	$165.38	$165.40	$165.40
7 purchase totals =	$924.86		$1,000.4101	$1,000.41	$1,000.40	$1,000.50