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	$160.27	11.260%	$178.3164	$178.32	$178.30	$178.30
Purchase #2	$200.91	8.212%	$217.4087	$217.41	$217.40	$217.40
Purchase #3	$80.53	6.698%	$85.9239	$85.92	$85.90	$85.90
Purchase #4	$79.57	13.162%	$90.043	$90.04	$90.05	$90.00
Purchase #5	$147.87	4.837%	$155.0225	$155.02	$155.00	$155.00
Purchase #6	$195.69	7.791%	$210.9362	$210.94	$210.95	$210.90
Purchase #7	$182.82	10.391%	$201.8168	$201.82	$201.80	$201.80
7 purchase totals =	$1,047.66		$1,139.4675	$1,139.47	$1,139.40	$1,139.30