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	$174.31	11.662%	$194.638	$194.64	$194.65	$194.60
Purchase #2	$215.46	6.620%	$229.7235	$229.72	$229.70	$229.70
Purchase #3	$35.43	6.835%	$37.8516	$37.85	$37.85	$37.90
Purchase #4	$246.98	5.259%	$259.9687	$259.97	$259.95	$260.00
Purchase #5	$61.40	13.871%	$69.9168	$69.92	$69.90	$69.90
Purchase #6	$136.92	13.215%	$155.014	$155.01	$155.00	$155.00
Purchase #7	$137.34	5.102%	$144.3471	$144.35	$144.35	$144.30
7 purchase totals =	$1,007.84		$1,091.4597	$1,091.46	$1,091.40	$1,091.40