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	$88.35	12.830%	$99.6853	$99.69	$99.70	$99.70
Purchase #2	$144.91	9.593%	$158.8112	$158.81	$158.80	$158.80
Purchase #3	$82.90	9.357%	$90.657	$90.66	$90.65	$90.70
Purchase #4	$248.83	3.737%	$258.1288	$258.13	$258.15	$258.10
Purchase #5	$67.61	7.323%	$72.5611	$72.56	$72.55	$72.60
Purchase #6	$156.54	5.297%	$164.8319	$164.83	$164.85	$164.80
Purchase #7	$170.64	5.717%	$180.3955	$180.40	$180.40	$180.40
7 purchase totals =	$959.78		$1,025.0708	$1,025.08	$1,025.10	$1,025.10