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	$69.56	8.411%	$75.4107	$75.41	$75.40	$75.40
Purchase #2	$174.30	6.609%	$185.8195	$185.82	$185.80	$185.80
Purchase #3	$250.90	3.564%	$259.8421	$259.84	$259.85	$259.80
Purchase #4	$98.46	5.537%	$103.9117	$103.91	$103.90	$103.90
Purchase #5	$102.86	8.817%	$111.9292	$111.93	$111.95	$111.90
Purchase #6	$210.55	6.572%	$224.3873	$224.39	$224.40	$224.40
Purchase #7	$152.93	7.571%	$164.5083	$164.51	$164.50	$164.50
7 purchase totals =	$1,059.56		$1,125.8088	$1,125.81	$1,125.80	$1,125.70