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	$157.88	8.789%	$171.7561	$171.76	$171.75	$171.80
Purchase #2	$196.44	10.819%	$217.6928	$217.69	$217.70	$217.70
Purchase #3	$22.88	12.807%	$25.8102	$25.81	$25.80	$25.80
Purchase #4	$131.98	6.864%	$141.0391	$141.04	$141.05	$141.00
Purchase #5	$150.42	6.663%	$160.4425	$160.44	$160.45	$160.40
Purchase #6	$246.45	7.532%	$265.0126	$265.01	$265.00	$265.00
Purchase #7	$185.59	8.192%	$200.7935	$200.79	$200.80	$200.80
7 purchase totals =	$1,091.64		$1,182.5468	$1,182.54	$1,182.55	$1,182.50