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	$97.97	8.135%	$105.9399	$105.94	$105.95	$105.90
Purchase #2	$136.89	13.628%	$155.5454	$155.55	$155.55	$155.50
Purchase #3	$119.71	7.809%	$129.0582	$129.06	$129.05	$129.10
Purchase #4	$112.30	10.343%	$123.9152	$123.92	$123.90	$123.90
Purchase #5	$62.77	8.262%	$67.9561	$67.96	$67.95	$68.00
Purchase #6	$98.95	4.792%	$103.6917	$103.69	$103.70	$103.70
Purchase #7	$54.50	4.679%	$57.0501	$57.05	$57.05	$57.10
7 purchase totals =	$683.09		$743.1566	$743.17	$743.15	$743.20