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	$185.99	5.862%	$196.8927	$196.89	$196.90	$196.90
Purchase #2	$95.43	3.311%	$98.5897	$98.59	$98.60	$98.60
Purchase #3	$60.82	7.850%	$65.5944	$65.59	$65.60	$65.60
Purchase #4	$164.64	3.597%	$170.5621	$170.56	$170.55	$170.60
Purchase #5	$89.31	4.457%	$93.2905	$93.29	$93.30	$93.30
Purchase #6	$107.81	3.655%	$111.7505	$111.75	$111.75	$111.80
Purchase #7	$39.58	13.398%	$44.8829	$44.88	$44.90	$44.90
7 purchase totals =	$743.58		$781.5628	$781.55	$781.60	$781.70