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	$86.44	11.197%	$96.1187	$96.12	$96.10	$96.10
Purchase #2	$91.39	13.440%	$103.6728	$103.67	$103.65	$103.70
Purchase #3	$55.40	4.589%	$57.9423	$57.94	$57.95	$57.90
Purchase #4	$116.46	13.142%	$131.7652	$131.77	$131.75	$131.80
Purchase #5	$238.41	10.846%	$264.2679	$264.27	$264.25	$264.30
Purchase #6	$94.38	11.131%	$104.8854	$104.89	$104.90	$104.90
Purchase #7	$18.34	4.670%	$19.1965	$19.20	$19.20	$19.20
7 purchase totals =	$700.82		$777.8488	$777.86	$777.80	$777.90