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	$82.79	11.137%	$92.0103	$92.01	$92.00	$92.00
Purchase #2	$124.94	9.663%	$137.013	$137.01	$137.00	$137.00
Purchase #3	$243.31	13.577%	$276.3442	$276.34	$276.35	$276.30
Purchase #4	$73.44	5.406%	$77.4102	$77.41	$77.40	$77.40
Purchase #5	$50.56	9.452%	$55.3389	$55.34	$55.35	$55.30
Purchase #6	$187.83	5.853%	$198.8237	$198.82	$198.80	$198.80
Purchase #7	$69.39	4.284%	$72.3627	$72.36	$72.35	$72.40
7 purchase totals =	$832.26		$909.3030	$909.29	$909.25	$909.20