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	$120.69	9.327%	$131.9468	$131.95	$131.95	$131.90
Purchase #2	$179.90	10.537%	$198.8561	$198.86	$198.85	$198.90
Purchase #3	$194.38	5.818%	$205.689	$205.69	$205.70	$205.70
Purchase #4	$35.77	4.442%	$37.3589	$37.36	$37.35	$37.40
Purchase #5	$105.54	8.409%	$114.4149	$114.41	$114.40	$114.40
Purchase #6	$90.31	9.644%	$99.0195	$99.02	$99.00	$99.00
Purchase #7	$223.99	7.481%	$240.7467	$240.75	$240.75	$240.70
7 purchase totals =	$950.58		$1,028.0319	$1,028.04	$1,028.00	$1,028.00