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	$152.70	3.717%	$158.3759	$158.38	$158.40	$158.40
Purchase #2	$113.25	6.692%	$120.8287	$120.83	$120.85	$120.80
Purchase #3	$35.46	6.126%	$37.6323	$37.63	$37.65	$37.60
Purchase #4	$167.89	6.466%	$178.7458	$178.75	$178.75	$178.70
Purchase #5	$52.47	12.793%	$59.1825	$59.18	$59.20	$59.20
Purchase #6	$111.79	10.668%	$123.7158	$123.72	$123.70	$123.70
Purchase #7	$246.66	7.209%	$264.4417	$264.44	$264.45	$264.40
7 purchase totals =	$880.22		$942.9227	$942.93	$943.00	$942.80