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	$77.71	11.759%	$86.8479	$86.85	$86.85	$86.80
Purchase #2	$183.71	13.156%	$207.8789	$207.88	$207.90	$207.90
Purchase #3	$45.41	3.387%	$46.948	$46.95	$46.95	$46.90
Purchase #4	$175.59	8.512%	$190.5362	$190.54	$190.55	$190.50
Purchase #5	$202.27	9.383%	$221.249	$221.25	$221.25	$221.20
Purchase #6	$78.74	10.274%	$86.8297	$86.83	$86.85	$86.80
Purchase #7	$215.25	12.535%	$242.2316	$242.23	$242.25	$242.20
7 purchase totals =	$978.68		$1,082.5213	$1,082.53	$1,082.60	$1,082.30