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	$139.48	3.345%	$144.1456	$144.15	$144.15	$144.10
Purchase #2	$175.87	6.272%	$186.9006	$186.90	$186.90	$186.90
Purchase #3	$158.44	4.681%	$165.8566	$165.86	$165.85	$165.90
Purchase #4	$60.82	10.728%	$67.3448	$67.34	$67.35	$67.30
Purchase #5	$178.80	11.510%	$199.3799	$199.38	$199.40	$199.40
Purchase #6	$201.96	6.822%	$215.7377	$215.74	$215.75	$215.70
Purchase #7	$119.68	6.864%	$127.8948	$127.89	$127.90	$127.90
7 purchase totals =	$1,035.05		$1,107.2600	$1,107.26	$1,107.30	$1,107.20