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	$151.69	10.694%	$167.9117	$167.91	$167.90	$167.90
Purchase #2	$133.72	13.787%	$152.156	$152.16	$152.15	$152.20
Purchase #3	$28.83	5.846%	$30.5154	$30.52	$30.50	$30.50
Purchase #4	$40.31	7.539%	$43.349	$43.35	$43.35	$43.30
Purchase #5	$207.69	12.395%	$233.4332	$233.43	$233.45	$233.40
Purchase #6	$160.34	11.382%	$178.5899	$178.59	$178.60	$178.60
Purchase #7	$197.75	3.355%	$204.3845	$204.38	$204.40	$204.40
7 purchase totals =	$920.33		$1,010.3397	$1,010.34	$1,010.35	$1,010.30