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	$32.69	3.639%	$33.8796	$33.88	$33.90	$33.90
Purchase #2	$168.29	12.859%	$189.9304	$189.93	$189.95	$189.90
Purchase #3	$208.54	7.837%	$224.8833	$224.88	$224.90	$224.90
Purchase #4	$56.44	9.182%	$61.6223	$61.62	$61.60	$61.60
Purchase #5	$42.80	5.834%	$45.297	$45.30	$45.30	$45.30
Purchase #6	$60.67	12.769%	$68.417	$68.42	$68.40	$68.40
Purchase #7	$97.73	12.125%	$109.5798	$109.58	$109.60	$109.60
7 purchase totals =	$667.16		$733.6094	$733.61	$733.65	$733.60