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	$112.83	3.773%	$117.0871	$117.09	$117.10	$117.10
Purchase #2	$22.71	10.604%	$25.1182	$25.12	$25.10	$25.10
Purchase #3	$171.91	6.206%	$182.5787	$182.58	$182.60	$182.60
Purchase #4	$185.53	10.836%	$205.634	$205.63	$205.65	$205.60
Purchase #5	$215.49	8.258%	$233.2852	$233.29	$233.30	$233.30
Purchase #6	$240.45	10.558%	$265.8367	$265.84	$265.85	$265.80
Purchase #7	$72.86	8.197%	$78.8323	$78.83	$78.85	$78.80
7 purchase totals =	$1,021.78		$1,108.3722	$1,108.38	$1,108.45	$1,108.30