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	$99.77	11.365%	$111.1089	$111.11	$111.10	$111.10
Purchase #2	$224.77	3.268%	$232.1155	$232.12	$232.10	$232.10
Purchase #3	$104.37	7.463%	$112.1591	$112.16	$112.15	$112.20
Purchase #4	$186.64	13.279%	$211.4239	$211.42	$211.40	$211.40
Purchase #5	$39.77	3.769%	$41.2689	$41.27	$41.25	$41.30
Purchase #6	$196.30	4.638%	$205.4044	$205.40	$205.40	$205.40
Purchase #7	$26.96	9.293%	$29.4654	$29.47	$29.45	$29.50
7 purchase totals =	$878.58		$942.9461	$942.95	$942.85	$943.00