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	$60.78	7.395%	$65.2747	$65.27	$65.25	$65.30
Purchase #2	$73.87	10.740%	$81.8036	$81.80	$81.80	$81.80
Purchase #3	$183.44	7.183%	$196.6165	$196.62	$196.60	$196.60
Purchase #4	$156.60	11.653%	$174.8486	$174.85	$174.85	$174.80
Purchase #5	$120.33	5.288%	$126.6931	$126.69	$126.70	$126.70
Purchase #6	$163.57	13.396%	$185.4818	$185.48	$185.50	$185.50
Purchase #7	$221.78	10.593%	$245.2732	$245.27	$245.25	$245.30
7 purchase totals =	$980.37		$1,075.9915	$1,075.98	$1,075.95	$1,076.00