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	$219.71	10.745%	$243.3178	$243.32	$243.30	$243.30
Purchase #2	$136.95	10.154%	$150.8559	$150.86	$150.85	$150.90
Purchase #3	$141.65	6.862%	$151.37	$151.37	$151.35	$151.40
Purchase #4	$52.48	7.645%	$56.4921	$56.49	$56.50	$56.50
Purchase #5	$181.48	6.131%	$192.6065	$192.61	$192.60	$192.60
Purchase #6	$170.83	9.126%	$186.4199	$186.42	$186.40	$186.40
Purchase #7	$65.43	7.507%	$70.3418	$70.34	$70.35	$70.30
7 purchase totals =	$968.53		$1,051.4040	$1,051.41	$1,051.35	$1,051.40