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	$118.72	10.288%	$130.9339	$130.93	$130.95	$130.90
Purchase #2	$169.39	11.518%	$188.9003	$188.90	$188.90	$188.90
Purchase #3	$71.92	10.105%	$79.1875	$79.19	$79.20	$79.20
Purchase #4	$24.76	13.236%	$28.0372	$28.04	$28.05	$28.00
Purchase #5	$40.41	3.840%	$41.9617	$41.96	$41.95	$42.00
Purchase #6	$41.87	4.164%	$43.6135	$43.61	$43.60	$43.60
Purchase #7	$76.52	11.665%	$85.4461	$85.45	$85.45	$85.40
7 purchase totals =	$543.59		$598.0802	$598.08	$598.10	$598.00