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	$33.67	5.540%	$35.5353	$35.54	$35.55	$35.50
Purchase #2	$179.81	11.690%	$200.8298	$200.83	$200.85	$200.80
Purchase #3	$188.71	11.435%	$210.289	$210.29	$210.30	$210.30
Purchase #4	$64.71	13.383%	$73.3701	$73.37	$73.35	$73.40
Purchase #5	$20.55	3.790%	$21.3288	$21.33	$21.35	$21.30
Purchase #6	$93.56	5.321%	$98.5383	$98.54	$98.55	$98.50
Purchase #7	$182.66	12.444%	$205.3902	$205.39	$205.40	$205.40
7 purchase totals =	$763.67		$845.2815	$845.29	$845.35	$845.20