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	$51.34	12.219%	$57.6132	$57.61	$57.60	$57.60
Purchase #2	$155.66	6.279%	$165.4339	$165.43	$165.45	$165.40
Purchase #3	$133.79	6.215%	$142.105	$142.11	$142.10	$142.10
Purchase #4	$162.77	10.253%	$179.4588	$179.46	$179.45	$179.50
Purchase #5	$227.42	7.854%	$245.2816	$245.28	$245.30	$245.30
Purchase #6	$164.76	12.781%	$185.818	$185.82	$185.80	$185.80
Purchase #7	$49.65	4.527%	$51.8977	$51.90	$51.90	$51.90
7 purchase totals =	$945.39		$1,027.6082	$1,027.61	$1,027.60	$1,027.60