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	$114.85	3.370%	$118.7204	$118.72	$118.70	$118.70
Purchase #2	$227.89	10.376%	$251.5359	$251.54	$251.55	$251.50
Purchase #3	$186.74	9.587%	$204.6428	$204.64	$204.65	$204.60
Purchase #4	$57.68	12.583%	$64.9379	$64.94	$64.95	$64.90
Purchase #5	$75.33	9.376%	$82.3929	$82.39	$82.40	$82.40
Purchase #6	$77.82	9.834%	$85.4728	$85.47	$85.45	$85.50
Purchase #7	$209.81	6.121%	$222.6525	$222.65	$222.65	$222.70
7 purchase totals =	$950.12		$1,030.3552	$1,030.35	$1,030.35	$1,030.30