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	$173.27	11.232%	$192.7317	$192.73	$192.75	$192.70
Purchase #2	$130.98	4.615%	$137.0247	$137.02	$137.00	$137.00
Purchase #3	$169.60	12.779%	$191.2732	$191.27	$191.25	$191.30
Purchase #4	$207.50	12.567%	$233.5765	$233.58	$233.60	$233.60
Purchase #5	$39.29	7.626%	$42.2863	$42.29	$42.30	$42.30
Purchase #6	$85.51	9.357%	$93.5112	$93.51	$93.50	$93.50
Purchase #7	$170.31	8.615%	$184.9822	$184.98	$185.00	$185.00
7 purchase totals =	$976.46		$1,075.3858	$1,075.38	$1,075.40	$1,075.40