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	$199.65	3.332%	$206.3023	$206.30	$206.30	$206.30
Purchase #2	$48.66	10.123%	$53.5859	$53.59	$53.60	$53.60
Purchase #3	$152.87	7.858%	$164.8825	$164.88	$164.90	$164.90
Purchase #4	$88.98	10.777%	$98.5694	$98.57	$98.55	$98.60
Purchase #5	$73.33	7.450%	$78.7931	$78.79	$78.80	$78.80
Purchase #6	$20.49	5.224%	$21.5604	$21.56	$21.55	$21.60
Purchase #7	$54.41	5.447%	$57.3737	$57.37	$57.35	$57.40
7 purchase totals =	$638.39		$681.0673	$681.06	$681.05	$681.20