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	$99.32	6.818%	$106.0916	$106.09	$106.10	$106.10
Purchase #2	$27.56	8.440%	$29.8861	$29.89	$29.90	$29.90
Purchase #3	$218.90	4.334%	$228.3871	$228.39	$228.40	$228.40
Purchase #4	$228.89	7.272%	$245.5349	$245.53	$245.55	$245.50
Purchase #5	$84.69	5.199%	$89.093	$89.09	$89.10	$89.10
Purchase #6	$154.58	12.451%	$173.8268	$173.83	$173.85	$173.80
Purchase #7	$127.43	13.570%	$144.7223	$144.72	$144.70	$144.70
7 purchase totals =	$941.37		$1,017.5418	$1,017.54	$1,017.60	$1,017.50