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	$89.85	9.389%	$98.286	$98.29	$98.30	$98.30
Purchase #2	$136.73	4.378%	$142.716	$142.72	$142.70	$142.70
Purchase #3	$215.33	4.667%	$225.3795	$225.38	$225.40	$225.40
Purchase #4	$188.33	13.560%	$213.8675	$213.87	$213.85	$213.90
Purchase #5	$159.50	3.251%	$164.6853	$164.69	$164.70	$164.70
Purchase #6	$5.25	12.312%	$5.8964	$5.90	$5.90	$5.90
Purchase #7	$162.94	4.274%	$169.9041	$169.90	$169.90	$169.90
7 purchase totals =	$957.93		$1,020.7348	$1,020.75	$1,020.75	$1,020.80